2 .\" Copyright Neil Brown and others.
3 .\" This program is free software; you can redistribute it and/or modify
4 .\" it under the terms of the GNU General Public License as published by
5 .\" the Free Software Foundation; either version 2 of the License, or
6 .\" (at your option) any later version.
7 .\" See file COPYING in distribution for details.
10 mdadm \- manage MD devices
16 .BI mdadm " [mode] <raiddevice> [options] <component-devices>"
19 RAID devices are virtual devices created from two or more
20 real block devices. This allows multiple devices (typically disk
21 drives or partitions thereof) to be combined into a single device to
22 hold (for example) a single filesystem.
23 Some RAID levels include redundancy and so can survive some degree of
26 Linux Software RAID devices are implemented through the md (Multiple
27 Devices) device driver.
29 Currently, Linux supports
46 is not a Software RAID mechanism, but does involve
48 each device is a path to one common physical storage device.
49 New installations should not use md/multipath as it is not well
50 supported and has no ongoing development. Use the Device Mapper based
51 multipath-tools instead.
54 is also not true RAID, and it only involves one device. It
55 provides a layer over a true device that can be used to inject faults.
60 is a collection of devices that are
61 managed as a set. This is similar to the set of devices connected to
62 a hardware RAID controller. The set of devices may contain a number
63 of different RAID arrays each utilising some (or all) of the blocks from a
64 number of the devices in the set. For example, two devices in a 5-device set
65 might form a RAID1 using the whole devices. The remaining three might
66 have a RAID5 over the first half of each device, and a RAID0 over the
71 there is one set of metadata that describes all of
72 the arrays in the container. So when
76 device, the device just represents the metadata. Other normal arrays (RAID1
77 etc) can be created inside the container.
80 mdadm has several major modes of operation:
83 Assemble the components of a previously created
84 array into an active array. Components can be explicitly given
85 or can be searched for.
87 checks that the components
88 do form a bona fide array, and can, on request, fiddle superblock
89 information so as to assemble a faulty array.
93 Build an array that doesn't have per-device metadata (superblocks). For these
96 cannot differentiate between initial creation and subsequent assembly
97 of an array. It also cannot perform any checks that appropriate
98 components have been requested. Because of this, the
100 mode should only be used together with a complete understanding of
105 Create a new array with per-device metadata (superblocks).
106 Appropriate metadata is written to each device, and then the array
107 comprising those devices is activated. A 'resync' process is started
108 to make sure that the array is consistent (e.g. both sides of a mirror
109 contain the same data) but the content of the device is left otherwise
111 The array can be used as soon as it has been created. There is no
112 need to wait for the initial resync to finish.
115 .B "Follow or Monitor"
116 Monitor one or more md devices and act on any state changes. This is
117 only meaningful for RAID1, 4, 5, 6, 10 or multipath arrays, as
118 only these have interesting state. RAID0 or Linear never have
119 missing, spare, or failed drives, so there is nothing to monitor.
123 Grow (or shrink) an array, or otherwise reshape it in some way.
124 Currently supported growth options including changing the active size
125 of component devices and changing the number of active devices in
126 Linear and RAID levels 0/1/4/5/6,
127 changing the RAID level between 0, 1, 5, and 6, and between 0 and 10,
128 changing the chunk size and layout for RAID 0,4,5,6,10 as well as adding or
129 removing a write-intent bitmap.
132 .B "Incremental Assembly"
133 Add a single device to an appropriate array. If the addition of the
134 device makes the array runnable, the array will be started.
135 This provides a convenient interface to a
137 system. As each device is detected,
139 has a chance to include it in some array as appropriate.
142 flag is passed in we will remove the device from any active array
143 instead of adding it.
149 in this mode, then any arrays within that container will be assembled
154 This is for doing things to specific components of an array such as
155 adding new spares and removing faulty devices.
159 This is an 'everything else' mode that supports operations on active
160 arrays, operations on component devices such as erasing old superblocks, and
161 information gathering operations.
162 .\"This mode allows operations on independent devices such as examine MD
163 .\"superblocks, erasing old superblocks and stopping active arrays.
167 This mode does not act on a specific device or array, but rather it
168 requests the Linux Kernel to activate any auto-detected arrays.
171 .SH Options for selecting a mode are:
174 .BR \-A ", " \-\-assemble
175 Assemble a pre-existing array.
178 .BR \-B ", " \-\-build
179 Build a legacy array without superblocks.
182 .BR \-C ", " \-\-create
186 .BR \-F ", " \-\-follow ", " \-\-monitor
192 .BR \-G ", " \-\-grow
193 Change the size or shape of an active array.
196 .BR \-I ", " \-\-incremental
197 Add/remove a single device to/from an appropriate array, and possibly start the array.
201 Request that the kernel starts any auto-detected arrays. This can only
204 is compiled into the kernel \(em not if it is a module.
205 Arrays can be auto-detected by the kernel if all the components are in
206 primary MS-DOS partitions with partition type
208 and all use v0.90 metadata.
209 In-kernel autodetect is not recommended for new installations. Using
211 to detect and assemble arrays \(em possibly in an
213 \(em is substantially more flexible and should be preferred.
216 If a device is given before any options, or if the first option is
222 then the MANAGE mode is assumed.
223 Anything other than these will cause the
227 .SH Options that are not mode-specific are:
230 .BR \-h ", " \-\-help
231 Display general help message or, after one of the above options, a
232 mode-specific help message.
236 Display more detailed help about command line parsing and some commonly
240 .BR \-V ", " \-\-version
241 Print version information for mdadm.
244 .BR \-v ", " \-\-verbose
245 Be more verbose about what is happening. This can be used twice to be
247 The extra verbosity currently only affects
248 .B \-\-detail \-\-scan
250 .BR "\-\-examine \-\-scan" .
253 .BR \-q ", " \-\-quiet
254 Avoid printing purely informative messages. With this,
256 will be silent unless there is something really important to report.
260 .BR \-f ", " \-\-force
261 Be more forceful about certain operations. See the various modes for
262 the exact meaning of this option in different contexts.
265 .BR \-c ", " \-\-config=
266 Specify the config file or directory. Default is to use
269 .BR /etc/mdadm.conf.d ,
270 or if those are missing then
271 .B /etc/mdadm/mdadm.conf
273 .BR /etc/mdadm/mdadm.conf.d .
274 If the config file given is
276 then nothing will be read, but
278 will act as though the config file contained exactly
280 .B " DEVICE partitions containers"
284 to find a list of devices to scan, and
286 to find a list of containers to examine.
289 is given for the config file, then
291 will act as though the config file were empty.
293 If the name given is of a directory, then
295 will collect all the files contained in the directory with a name ending
298 sort them lexically, and process all of those files as config files.
301 .BR \-s ", " \-\-scan
304 for missing information.
305 In general, this option gives
307 permission to get any missing information (like component devices,
308 array devices, array identities, and alert destination) from the
309 configuration file (see previous option);
310 one exception is MISC mode when using
316 says to get a list of array devices from
320 .BR \-e ", " \-\-metadata=
321 Declare the style of RAID metadata (superblock) to be used. The
322 default is {DEFAULT_METADATA} for
324 and to guess for other operations.
325 The default can be overridden by setting the
334 .ie '{DEFAULT_METADATA}'0.90'
335 .IP "0, 0.90, default"
338 Use the original 0.90 format superblock. This format limits arrays to
339 28 component devices and limits component devices of levels 1 and
340 greater to 2 terabytes. It is also possible for there to be confusion
341 about whether the superblock applies to a whole device or just the
342 last partition, if that partition starts on a 64K boundary.
343 .ie '{DEFAULT_METADATA}'0.90'
344 .IP "1, 1.0, 1.1, 1.2"
346 .IP "1, 1.0, 1.1, 1.2 default"
347 Use the new version-1 format superblock. This has fewer restrictions.
348 It can easily be moved between hosts with different endian-ness, and a
349 recovery operation can be checkpointed and restarted. The different
350 sub-versions store the superblock at different locations on the
351 device, either at the end (for 1.0), at the start (for 1.1) or 4K from
352 the start (for 1.2). "1" is equivalent to "1.2" (the commonly
353 preferred 1.x format).
354 'if '{DEFAULT_METADATA}'1.2' "default" is equivalent to "1.2".
356 Use the "Industry Standard" DDF (Disk Data Format) format defined by
358 When creating a DDF array a
360 will be created, and normal arrays can be created in that container.
362 Use the Intel(R) Matrix Storage Manager metadata format. This creates a
364 which is managed in a similar manner to DDF, and is supported by an
365 option-rom on some platforms:
367 .B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
373 This will override any
375 setting in the config file and provides the identity of the host which
376 should be considered the home for any arrays.
378 When creating an array, the
380 will be recorded in the metadata. For version-1 superblocks, it will
381 be prefixed to the array name. For version-0.90 superblocks, part of
382 the SHA1 hash of the hostname will be stored in the later half of the
385 When reporting information about an array, any array which is tagged
386 for the given homehost will be reported as such.
388 When using Auto-Assemble, only arrays tagged for the given homehost
389 will be allowed to use 'local' names (i.e. not ending in '_' followed
390 by a digit string). See below under
391 .BR "Auto Assembly" .
397 needs to print the name for a device it normally finds the name in
399 which refers to the device and is shortest. When a path component is
403 will prefer a longer name if it contains that component. For example
404 .B \-\-prefer=by-uuid
405 will prefer a name in a subdirectory of
410 This functionality is currently only provided by
415 .SH For create, build, or grow:
418 .BR \-n ", " \-\-raid\-devices=
419 Specify the number of active devices in the array. This, plus the
420 number of spare devices (see below) must equal the number of
422 (including "\fBmissing\fP" devices)
423 that are listed on the command line for
425 Setting a value of 1 is probably
426 a mistake and so requires that
428 be specified first. A value of 1 will then be allowed for linear,
429 multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.
431 This number can only be changed using
433 for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide
434 the necessary support.
437 .BR \-x ", " \-\-spare\-devices=
438 Specify the number of spare (eXtra) devices in the initial array.
439 Spares can also be added
440 and removed later. The number of component devices listed
441 on the command line must equal the number of RAID devices plus the
442 number of spare devices.
445 .BR \-z ", " \-\-size=
446 Amount (in Kibibytes) of space to use from each drive in RAID levels 1/4/5/6.
447 This must be a multiple of the chunk size, and must leave about 128Kb
448 of space at the end of the drive for the RAID superblock.
449 If this is not specified
450 (as it normally is not) the smallest drive (or partition) sets the
451 size, though if there is a variance among the drives of greater than 1%, a warning is
454 A suffix of 'M' or 'G' can be given to indicate Megabytes or
455 Gigabytes respectively.
457 Sometimes a replacement drive can be a little smaller than the
458 original drives though this should be minimised by IDEMA standards.
459 Such a replacement drive will be rejected by
461 To guard against this it can be useful to set the initial size
462 slightly smaller than the smaller device with the aim that it will
463 still be larger than any replacement.
465 This value can be set with
467 for RAID level 1/4/5/6 though
469 based arrays such as those with IMSM metadata may not be able to
471 If the array was created with a size smaller than the currently
472 active drives, the extra space can be accessed using
474 The size can be given as
476 which means to choose the largest size that fits on all current drives.
478 Before reducing the size of the array (with
479 .BR "\-\-grow \-\-size=" )
480 you should make sure that space isn't needed. If the device holds a
481 filesystem, you would need to resize the filesystem to use less space.
483 After reducing the array size you should check that the data stored in
484 the device is still available. If the device holds a filesystem, then
485 an 'fsck' of the filesystem is a minimum requirement. If there are
486 problems the array can be made bigger again with no loss with another
487 .B "\-\-grow \-\-size="
490 This value cannot be used when creating a
492 such as with DDF and IMSM metadata, though it perfectly valid when
493 creating an array inside a container.
496 .BR \-Z ", " \-\-array\-size=
497 This is only meaningful with
499 and its effect is not persistent: when the array is stopped and
500 restarted the default array size will be restored.
502 Setting the array-size causes the array to appear smaller to programs
503 that access the data. This is particularly needed before reshaping an
504 array so that it will be smaller. As the reshape is not reversible,
505 but setting the size with
507 is, it is required that the array size is reduced as appropriate
508 before the number of devices in the array is reduced.
510 Before reducing the size of the array you should make sure that space
511 isn't needed. If the device holds a filesystem, you would need to
512 resize the filesystem to use less space.
514 After reducing the array size you should check that the data stored in
515 the device is still available. If the device holds a filesystem, then
516 an 'fsck' of the filesystem is a minimum requirement. If there are
517 problems the array can be made bigger again with no loss with another
518 .B "\-\-grow \-\-array\-size="
521 A suffix of 'M' or 'G' can be given to indicate Megabytes or
522 Gigabytes respectively.
525 restores the apparent size of the array to be whatever the real
526 amount of available space is.
529 .BR \-c ", " \-\-chunk=
530 Specify chunk size of kibibytes. The default when creating an
531 array is 512KB. To ensure compatibility with earlier versions, the
532 default when Building and array with no persistent metadata is 64KB.
533 This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
535 RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power
536 of 2. In any case it must be a multiple of 4KB.
538 A suffix of 'M' or 'G' can be given to indicate Megabytes or
539 Gigabytes respectively.
543 Specify rounding factor for a Linear array. The size of each
544 component will be rounded down to a multiple of this size.
545 This is a synonym for
547 but highlights the different meaning for Linear as compared to other
548 RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
549 use, and is 0K (i.e. no rounding) in later kernels.
552 .BR \-l ", " \-\-level=
553 Set RAID level. When used with
555 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
556 raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
557 Obviously some of these are synonymous.
561 metadata type is requested, only the
563 level is permitted, and it does not need to be explicitly given.
567 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
571 to change the RAID level in some cases. See LEVEL CHANGES below.
574 .BR \-p ", " \-\-layout=
575 This option configures the fine details of data layout for RAID5, RAID6,
576 and RAID10 arrays, and controls the failure modes for
579 The layout of the RAID5 parity block can be one of
580 .BR left\-asymmetric ,
581 .BR left\-symmetric ,
582 .BR right\-asymmetric ,
583 .BR right\-symmetric ,
584 .BR la ", " ra ", " ls ", " rs .
586 .BR left\-symmetric .
588 It is also possible to cause RAID5 to use a RAID4-like layout by
594 Finally for RAID5 there are DDF\-compatible layouts,
595 .BR ddf\-zero\-restart ,
596 .BR ddf\-N\-restart ,
598 .BR ddf\-N\-continue .
600 These same layouts are available for RAID6. There are also 4 layouts
601 that will provide an intermediate stage for converting between RAID5
602 and RAID6. These provide a layout which is identical to the
603 corresponding RAID5 layout on the first N\-1 devices, and has the 'Q'
604 syndrome (the second 'parity' block used by RAID6) on the last device.
606 .BR left\-symmetric\-6 ,
607 .BR right\-symmetric\-6 ,
608 .BR left\-asymmetric\-6 ,
609 .BR right\-asymmetric\-6 ,
611 .BR parity\-first\-6 .
613 When setting the failure mode for level
616 .BR write\-transient ", " wt ,
617 .BR read\-transient ", " rt ,
618 .BR write\-persistent ", " wp ,
619 .BR read\-persistent ", " rp ,
621 .BR read\-fixable ", " rf ,
622 .BR clear ", " flush ", " none .
624 Each failure mode can be followed by a number, which is used as a period
625 between fault generation. Without a number, the fault is generated
626 once on the first relevant request. With a number, the fault will be
627 generated after that many requests, and will continue to be generated
628 every time the period elapses.
630 Multiple failure modes can be current simultaneously by using the
632 option to set subsequent failure modes.
634 "clear" or "none" will remove any pending or periodic failure modes,
635 and "flush" will clear any persistent faults.
637 Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
638 by a small number. The default is 'n2'. The supported options are:
641 signals 'near' copies. Multiple copies of one data block are at
642 similar offsets in different devices.
645 signals 'offset' copies. Rather than the chunks being duplicated
646 within a stripe, whole stripes are duplicated but are rotated by one
647 device so duplicate blocks are on different devices. Thus subsequent
648 copies of a block are in the next drive, and are one chunk further
653 (multiple copies have very different offsets).
654 See md(4) for more detail about 'near', 'offset', and 'far'.
656 The number is the number of copies of each datablock. 2 is normal, 3
657 can be useful. This number can be at most equal to the number of
658 devices in the array. It does not need to divide evenly into that
659 number (e.g. it is perfectly legal to have an 'n2' layout for an array
660 with an odd number of devices).
662 When an array is converted between RAID5 and RAID6 an intermediate
663 RAID6 layout is used in which the second parity block (Q) is always on
664 the last device. To convert a RAID5 to RAID6 and leave it in this new
665 layout (which does not require re-striping) use
666 .BR \-\-layout=preserve .
667 This will try to avoid any restriping.
669 The converse of this is
670 .B \-\-layout=normalise
671 which will change a non-standard RAID6 layout into a more standard
678 (thus explaining the p of
682 .BR \-b ", " \-\-bitmap=
683 Specify a file to store a write-intent bitmap in. The file should not
686 is also given. The same file should be provided
687 when assembling the array. If the word
689 is given, then the bitmap is stored with the metadata on the array,
690 and so is replicated on all devices. If the word
694 mode, then any bitmap that is present is removed.
696 To help catch typing errors, the filename must contain at least one
697 slash ('/') if it is a real file (not 'internal' or 'none').
699 Note: external bitmaps are only known to work on ext2 and ext3.
700 Storing bitmap files on other filesystems may result in serious problems.
702 When creating an array on devices which are 100G or larger,
704 automatically adds an internal bitmap as it will usually be
705 beneficial. This can be suppressed with
706 .B "\-\-bitmap=none".
709 .BR \-\-bitmap\-chunk=
710 Set the chunksize of the bitmap. Each bit corresponds to that many
711 Kilobytes of storage.
712 When using a file based bitmap, the default is to use the smallest
713 size that is at-least 4 and requires no more than 2^21 chunks.
716 bitmap, the chunksize defaults to 64Meg, or larger if necessary to
717 fit the bitmap into the available space.
719 A suffix of 'M' or 'G' can be given to indicate Megabytes or
720 Gigabytes respectively.
723 .BR \-W ", " \-\-write\-mostly
724 subsequent devices listed in a
729 command will be flagged as 'write-mostly'. This is valid for RAID1
730 only and means that the 'md' driver will avoid reading from these
731 devices if at all possible. This can be useful if mirroring over a
735 .BR \-\-write\-behind=
736 Specify that write-behind mode should be enabled (valid for RAID1
737 only). If an argument is specified, it will set the maximum number
738 of outstanding writes allowed. The default value is 256.
739 A write-intent bitmap is required in order to use write-behind
740 mode, and write-behind is only attempted on drives marked as
744 .BR \-\-assume\-clean
747 that the array pre-existed and is known to be clean. It can be useful
748 when trying to recover from a major failure as you can be sure that no
749 data will be affected unless you actually write to the array. It can
750 also be used when creating a RAID1 or RAID10 if you want to avoid the
751 initial resync, however this practice \(em while normally safe \(em is not
752 recommended. Use this only if you really know what you are doing.
754 When the devices that will be part of a new array were filled
755 with zeros before creation the operator knows the array is
756 actually clean. If that is the case, such as after running
757 badblocks, this argument can be used to tell mdadm the
758 facts the operator knows.
760 When an array is resized to a larger size with
761 .B "\-\-grow \-\-size="
762 the new space is normally resynced in that same way that the whole
763 array is resynced at creation. From Linux version 3.0,
765 can be used with that command to avoid the automatic resync.
768 .BR \-\-backup\-file=
771 is used to increase the number of raid-devices in a RAID5 or RAID6 if
772 there are no spare devices available, or to shrink, change RAID level
773 or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
774 The file must be stored on a separate device, not on the RAID array
779 Arrays with 1.x metadata can leave a gap between the start of the
780 device and the start of array data. This gap can be used for various
781 metadata. The start of data is known as the
783 Normally an appropriate data offset is computed automatically.
784 However it can be useful to set it explicitly such as when re-creating
785 an array which was originally created using a different version of
787 which computed a different offset.
789 Setting the offset explicitly over-rides the default. The value given
790 is in Kilobytes unless an 'M' or 'G' suffix is given.
794 can also be used with
796 for some RAID levels (initially on RAID10). This allows the
797 data\-offset to be changed as part of the reshape process. When the
798 data offset is changed, no backup file is required as the difference
799 in offsets is used to provide the same functionality.
801 When the new offset is earlier than the old offset, the number of
802 devices in the array cannot shrink. When it is after the old offset,
803 the number of devices in the array cannot increase.
805 When creating an array,
809 In the case each member device is expected to have a offset appended
810 to the name, separated by a colon. This makes it possible to recreate
811 exactly an array which has varying data offsets (as can happen when
812 different versions of
814 are used to add different devices).
818 This option is complementary to the
819 .B \-\-freeze-reshape
820 option for assembly. It is needed when
822 operation is interrupted and it is not restarted automatically due to
823 .B \-\-freeze-reshape
824 usage during array assembly. This option is used together with
828 ) command and device for a pending reshape to be continued.
829 All parameters required for reshape continuation will be read from array metadata.
833 .BR \-\-backup\-file=
834 option to be set, continuation option will require to have exactly the same
835 backup file given as well.
837 Any other parameter passed together with
839 option will be ignored.
842 .BR \-N ", " \-\-name=
845 for the array. This is currently only effective when creating an
846 array with a version-1 superblock, or an array in a DDF container.
847 The name is a simple textual string that can be used to identify array
848 components when assembling. If name is needed but not specified, it
849 is taken from the basename of the device that is being created.
861 run the array, even if some of the components
862 appear to be active in another array or filesystem. Normally
864 will ask for confirmation before including such components in an
865 array. This option causes that question to be suppressed.
868 .BR \-f ", " \-\-force
871 accept the geometry and layout specified without question. Normally
873 will not allow creation of an array with only one device, and will try
874 to create a RAID5 array with one missing drive (as this makes the
875 initial resync work faster). With
878 will not try to be so clever.
881 .BR \-o ", " \-\-readonly
884 rather than read-write as normal. No writes will be allowed to the
885 array, and no resync, recovery, or reshape will be started.
888 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
889 Instruct mdadm how to create the device file if needed, possibly allocating
890 an unused minor number. "md" causes a non-partitionable array
891 to be used (though since Linux 2.6.28, these array devices are in fact
892 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
893 later) to be used. "yes" requires the named md device to have
894 a 'standard' format, and the type and minor number will be determined
895 from this. With mdadm 3.0, device creation is normally left up to
897 so this option is unlikely to be needed.
898 See DEVICE NAMES below.
900 The argument can also come immediately after
905 is not given on the command line or in the config file, then
911 is also given, then any
913 entries in the config file will override the
915 instruction given on the command line.
917 For partitionable arrays,
919 will create the device file for the whole array and for the first 4
920 partitions. A different number of partitions can be specified at the
921 end of this option (e.g.
923 If the device name ends with a digit, the partition names add a 'p',
925 .IR /dev/md/home1p3 .
926 If there is no trailing digit, then the partition names just have a
928 .IR /dev/md/scratch3 .
930 If the md device name is in a 'standard' format as described in DEVICE
931 NAMES, then it will be created, if necessary, with the appropriate
932 device number based on that name. If the device name is not in one of these
933 formats, then a unused device number will be allocated. The device
934 number will be considered unused if there is no active array for that
935 number, and there is no entry in /dev for that number and with a
936 non-standard name. Names that are not in 'standard' format are only
937 allowed in "/dev/md/".
939 This is meaningful with
945 .BR \-a ", " "\-\-add"
946 This option can be used in Grow mode in two cases.
948 If the target array is a Linear array, then
950 can be used to add one or more devices to the array. They
951 are simply catenated on to the end of the array. Once added, the
952 devices cannot be removed.
956 option is being used to increase the number of devices in an array,
959 can be used to add some extra devices to be included in the array.
960 In most cases this is not needed as the extra devices can be added as
961 spares first, and then the number of raid-disks can be changed.
962 However for RAID0, it is not possible to add spares. So to increase
963 the number of devices in a RAID0, it is necessary to set the new
964 number of devices, and to add the new devices, in the same command.
969 .BR \-u ", " \-\-uuid=
970 uuid of array to assemble. Devices which don't have this uuid are
974 .BR \-m ", " \-\-super\-minor=
975 Minor number of device that array was created for. Devices which
976 don't have this minor number are excluded. If you create an array as
977 /dev/md1, then all superblocks will contain the minor number 1, even if
978 the array is later assembled as /dev/md2.
980 Giving the literal word "dev" for
984 to use the minor number of the md device that is being assembled.
987 .B \-\-super\-minor=dev
988 will look for super blocks with a minor number of 0.
991 is only relevant for v0.90 metadata, and should not normally be used.
997 .BR \-N ", " \-\-name=
998 Specify the name of the array to assemble. This must be the name
999 that was specified when creating the array. It must either match
1000 the name stored in the superblock exactly, or it must match
1003 prefixed to the start of the given name.
1006 .BR \-f ", " \-\-force
1007 Assemble the array even if the metadata on some devices appears to be
1010 cannot find enough working devices to start the array, but can find
1011 some devices that are recorded as having failed, then it will mark
1012 those devices as working so that the array can be started.
1013 An array which requires
1015 to be started may contain data corruption. Use it carefully.
1018 .BR \-R ", " \-\-run
1019 Attempt to start the array even if fewer drives were given than were
1020 present last time the array was active. Normally if not all the
1021 expected drives are found and
1023 is not used, then the array will be assembled but not started.
1026 an attempt will be made to start it anyway.
1030 This is the reverse of
1032 in that it inhibits the startup of array unless all expected drives
1033 are present. This is only needed with
1035 and can be used if the physical connections to devices are
1036 not as reliable as you would like.
1039 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
1040 See this option under Create and Build options.
1043 .BR \-b ", " \-\-bitmap=
1044 Specify the bitmap file that was given when the array was created. If
1047 bitmap, there is no need to specify this when assembling the array.
1050 .BR \-\-backup\-file=
1053 was used while reshaping an array (e.g. changing number of devices or
1054 chunk size) and the system crashed during the critical section, then the same
1056 must be presented to
1058 to allow possibly corrupted data to be restored, and the reshape
1062 .BR \-\-invalid\-backup
1063 If the file needed for the above option is not available for any
1064 reason an empty file can be given together with this option to
1065 indicate that the backup file is invalid. In this case the data that
1066 was being rearranged at the time of the crash could be irrecoverably
1067 lost, but the rest of the array may still be recoverable. This option
1068 should only be used as a last resort if there is no way to recover the
1073 .BR \-U ", " \-\-update=
1074 Update the superblock on each device while assembling the array. The
1075 argument given to this flag can be one of
1093 option will adjust the superblock of an array what was created on a Sparc
1094 machine running a patched 2.2 Linux kernel. This kernel got the
1095 alignment of part of the superblock wrong. You can use the
1096 .B "\-\-examine \-\-sparc2.2"
1099 to see what effect this would have.
1103 option will update the
1104 .B "preferred minor"
1105 field on each superblock to match the minor number of the array being
1107 This can be useful if
1109 reports a different "Preferred Minor" to
1111 In some cases this update will be performed automatically
1112 by the kernel driver. In particular the update happens automatically
1113 at the first write to an array with redundancy (RAID level 1 or
1114 greater) on a 2.6 (or later) kernel.
1118 option will change the uuid of the array. If a UUID is given with the
1120 option that UUID will be used as a new UUID and will
1122 be used to help identify the devices in the array.
1125 is given, a random UUID is chosen.
1129 option will change the
1131 of the array as stored in the superblock. This is only supported for
1132 version-1 superblocks.
1136 option will change the
1138 as recorded in the superblock. For version-0 superblocks, this is the
1139 same as updating the UUID.
1140 For version-1 superblocks, this involves updating the name.
1144 option will cause the array to be marked
1146 meaning that any redundancy in the array (e.g. parity for RAID5,
1147 copies for RAID1) may be incorrect. This will cause the RAID system
1148 to perform a "resync" pass to make sure that all redundant information
1153 option allows arrays to be moved between machines with different
1155 When assembling such an array for the first time after a move, giving
1156 .B "\-\-update=byteorder"
1159 to expect superblocks to have their byteorder reversed, and will
1160 correct that order before assembling the array. This is only valid
1161 with original (Version 0.90) superblocks.
1165 option will correct the summaries in the superblock. That is the
1166 counts of total, working, active, failed, and spare devices.
1170 option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1171 only (where the metadata is at the start of the device) and is only
1172 useful when the component device has changed size (typically become
1173 larger). The version 1 metadata records the amount of the device that
1174 can be used to store data, so if a device in a version 1.1 or 1.2
1175 array becomes larger, the metadata will still be visible, but the
1176 extra space will not. In this case it might be useful to assemble the
1178 .BR \-\-update=devicesize .
1181 to determine the maximum usable amount of space on each device and
1182 update the relevant field in the metadata.
1186 option only works on v0.90 metadata arrays and will convert them to
1187 v1.0 metadata. The array must not be dirty (i.e. it must not need a
1188 sync) and it must not have a write-intent bitmap.
1190 The old metadata will remain on the devices, but will appear older
1191 than the new metadata and so will usually be ignored. The old metadata
1192 (or indeed the new metadata) can be removed by giving the appropriate
1195 .BR \-\-zero\-superblock .
1199 option can be used when an array has an internal bitmap which is
1200 corrupt in some way so that assembling the array normally fails. It
1201 will cause any internal bitmap to be ignored.
1205 option will reserve space in each device for a bad block list. This
1206 will be 4K in size and positioned near the end of any free space
1207 between the superblock and the data.
1211 option will cause any reservation of space for a bad block list to be
1212 removed. If the bad block list contains entries, this will fail, as
1213 removing the list could cause data corruption.
1216 .BR \-\-freeze\-reshape
1217 Option is intended to be used in start-up scripts during initrd boot phase.
1218 When array under reshape is assembled during initrd phase, this option
1219 stops reshape after reshape critical section is being restored. This happens
1220 before file system pivot operation and avoids loss of file system context.
1221 Losing file system context would cause reshape to be broken.
1223 Reshape can be continued later using the
1225 option for the grow command.
1227 .SH For Manage mode:
1230 .BR \-t ", " \-\-test
1231 Unless a more serious error occurred,
1233 will exit with a status of 2 if no changes were made to the array and
1234 0 if at least one change was made.
1235 This can be useful when an indirect specifier such as
1240 is used in requesting an operation on the array.
1242 will report failure if these specifiers didn't find any match.
1245 .BR \-a ", " \-\-add
1246 hot-add listed devices.
1247 If a device appears to have recently been part of the array
1248 (possibly it failed or was removed) the device is re\-added as described
1250 If that fails or the device was never part of the array, the device is
1251 added as a hot-spare.
1252 If the array is degraded, it will immediately start to rebuild data
1255 Note that this and the following options are only meaningful on array
1256 with redundancy. They don't apply to RAID0 or Linear.
1260 re\-add a device that was previously removed from an array.
1261 If the metadata on the device reports that it is a member of the
1262 array, and the slot that it used is still vacant, then the device will
1263 be added back to the array in the same position. This will normally
1264 cause the data for that device to be recovered. However based on the
1265 event count on the device, the recovery may only require sections that
1266 are flagged a write-intent bitmap to be recovered or may not require
1267 any recovery at all.
1269 When used on an array that has no metadata (i.e. it was built with
1271 it will be assumed that bitmap-based recovery is enough to make the
1272 device fully consistent with the array.
1274 When used with v1.x metadata,
1276 can be accompanied by
1277 .BR \-\-update=devicesize ,
1278 .BR \-\-update=bbl ", or"
1279 .BR \-\-update=no\-bbl .
1280 See the description of these option when used in Assemble mode for an
1281 explanation of their use.
1283 If the device name given is
1287 will try to find any device that looks like it should be
1288 part of the array but isn't and will try to re\-add all such devices.
1290 If the device name given is
1294 will find all devices in the array that are marked
1296 remove them and attempt to immediately re\-add them. This can be
1297 useful if you are certain that the reason for failure has been
1301 .BR \-r ", " \-\-remove
1302 remove listed devices. They must not be active. i.e. they should
1303 be failed or spare devices.
1305 As well as the name of a device file
1315 The first causes all failed device to be removed. The second causes
1316 any device which is no longer connected to the system (i.e an 'open'
1320 The third will remove a set as describe below under
1324 .BR \-f ", " \-\-fail
1325 Mark listed devices as faulty.
1326 As well as the name of a device file, the word
1330 can be given. The former will cause any device that has been detached from
1331 the system to be marked as failed. It can then be removed.
1333 For RAID10 arrays where the number of copies evenly divides the number
1334 of devices, the devices can be conceptually divided into sets where
1335 each set contains a single complete copy of the data on the array.
1336 Sometimes a RAID10 array will be configured so that these sets are on
1337 separate controllers. In this case all the devices in one set can be
1338 failed by giving a name like
1344 The appropriate set names are reported by
1354 Mark listed devices as requiring replacement. As soon as a spare is
1355 available, it will be rebuilt and will replace the marked device.
1356 This is similar to marking a device as faulty, but the device remains
1357 in service during the recovery process to increase resilience against
1358 multiple failures. When the replacement process finishes, the
1359 replaced device will be marked as faulty.
1363 This can follow a list of
1365 devices. The devices listed after
1367 will be preferentially used to replace the devices listed after
1369 These device must already be spare devices in the array.
1372 .BR \-\-write\-mostly
1373 Subsequent devices that are added or re\-added will have the 'write-mostly'
1374 flag set. This is only valid for RAID1 and means that the 'md' driver
1375 will avoid reading from these devices if possible.
1378 Subsequent devices that are added or re\-added will have the 'write-mostly'
1382 Each of these options requires that the first device listed is the array
1383 to be acted upon, and the remainder are component devices to be added,
1384 removed, marked as faulty, etc. Several different operations can be
1385 specified for different devices, e.g.
1387 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1389 Each operation applies to all devices listed until the next
1392 If an array is using a write-intent bitmap, then devices which have
1393 been removed can be re\-added in a way that avoids a full
1394 reconstruction but instead just updates the blocks that have changed
1395 since the device was removed. For arrays with persistent metadata
1396 (superblocks) this is done automatically. For arrays created with
1398 mdadm needs to be told that this device we removed recently with
1401 Devices can only be removed from an array if they are not in active
1402 use, i.e. that must be spares or failed devices. To remove an active
1403 device, it must first be marked as
1409 .BR \-Q ", " \-\-query
1410 Examine a device to see
1411 (1) if it is an md device and (2) if it is a component of an md
1413 Information about what is discovered is presented.
1416 .BR \-D ", " \-\-detail
1417 Print details of one or more md devices.
1420 .BR \-\-detail\-platform
1421 Print details of the platform's RAID capabilities (firmware / hardware
1422 topology) for a given metadata format. If used without argument, mdadm
1423 will scan all controllers looking for their capabilities. Otherwise, mdadm
1424 will only look at the controller specified by the argument in form of an
1425 absolute filepath or a link, e.g.
1426 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1429 .BR \-Y ", " \-\-export
1431 .B \-\-detail , \-\-detail-platform
1434 output will be formatted as
1436 pairs for easy import into the environment.
1439 .BR \-E ", " \-\-examine
1440 Print contents of the metadata stored on the named device(s).
1441 Note the contrast between
1446 applies to devices which are components of an array, while
1448 applies to a whole array which is currently active.
1451 If an array was created on a SPARC machine with a 2.2 Linux kernel
1452 patched with RAID support, the superblock will have been created
1453 incorrectly, or at least incompatibly with 2.4 and later kernels.
1458 will fix the superblock before displaying it. If this appears to do
1459 the right thing, then the array can be successfully assembled using
1460 .BR "\-\-assemble \-\-update=sparc2.2" .
1463 .BR \-X ", " \-\-examine\-bitmap
1464 Report information about a bitmap file.
1465 The argument is either an external bitmap file or an array component
1466 in case of an internal bitmap. Note that running this on an array
1469 does not report the bitmap for that array.
1472 .B \-\-examine\-badblocks
1473 List the bad-blocks recorded for the device, if a bad-blocks list has
1474 been configured. Currently only
1476 metadata supports bad-blocks lists.
1479 .BI \-\-dump= directory
1481 .BI \-\-restore= directory
1482 Save metadata from lists devices, or restore metadata to listed devices.
1485 .BR \-R ", " \-\-run
1486 start a partially assembled array. If
1488 did not find enough devices to fully start the array, it might leaving
1489 it partially assembled. If you wish, you can then use
1491 to start the array in degraded mode.
1494 .BR \-S ", " \-\-stop
1495 deactivate array, releasing all resources.
1498 .BR \-o ", " \-\-readonly
1499 mark array as readonly.
1502 .BR \-w ", " \-\-readwrite
1503 mark array as readwrite.
1506 .B \-\-zero\-superblock
1507 If the device contains a valid md superblock, the block is
1508 overwritten with zeros. With
1510 the block where the superblock would be is overwritten even if it
1511 doesn't appear to be valid.
1514 .B \-\-kill\-subarray=
1515 If the device is a container and the argument to \-\-kill\-subarray
1516 specifies an inactive subarray in the container, then the subarray is
1517 deleted. Deleting all subarrays will leave an 'empty-container' or
1518 spare superblock on the drives. See
1519 .B \-\-zero\-superblock
1521 removing a superblock. Note that some formats depend on the subarray
1522 index for generating a UUID, this command will fail if it would change
1523 the UUID of an active subarray.
1526 .B \-\-update\-subarray=
1527 If the device is a container and the argument to \-\-update\-subarray
1528 specifies a subarray in the container, then attempt to update the given
1529 superblock field in the subarray. See below in
1534 .BR \-t ", " \-\-test
1539 is set to reflect the status of the device. See below in
1544 .BR \-W ", " \-\-wait
1545 For each md device given, wait for any resync, recovery, or reshape
1546 activity to finish before returning.
1548 will return with success if it actually waited for every device
1549 listed, otherwise it will return failure.
1553 For each md device given, or each device in /proc/mdstat if
1555 is given, arrange for the array to be marked clean as soon as possible.
1557 will return with success if the array uses external metadata and we
1558 successfully waited. For native arrays this returns immediately as the
1559 kernel handles dirty-clean transitions at shutdown. No action is taken
1560 if safe-mode handling is disabled.
1562 .SH For Incremental Assembly mode:
1564 .BR \-\-rebuild\-map ", " \-r
1565 Rebuild the map file
1569 uses to help track which arrays are currently being assembled.
1572 .BR \-\-run ", " \-R
1573 Run any array assembled as soon as a minimal number of devices are
1574 available, rather than waiting until all expected devices are present.
1577 .BR \-\-scan ", " \-s
1578 Only meaningful with
1582 file for arrays that are being incrementally assembled and will try to
1583 start any that are not already started. If any such array is listed
1586 as requiring an external bitmap, that bitmap will be attached first.
1589 .BR \-\-fail ", " \-f
1590 This allows the hot-plug system to remove devices that have fully disappeared
1591 from the kernel. It will first fail and then remove the device from any
1592 array it belongs to.
1593 The device name given should be a kernel device name such as "sda",
1599 Only used with \-\-fail. The 'path' given will be recorded so that if
1600 a new device appears at the same location it can be automatically
1601 added to the same array. This allows the failed device to be
1602 automatically replaced by a new device without metadata if it appears
1603 at specified path. This option is normally only set by a
1607 .SH For Monitor mode:
1609 .BR \-m ", " \-\-mail
1610 Give a mail address to send alerts to.
1613 .BR \-p ", " \-\-program ", " \-\-alert
1614 Give a program to be run whenever an event is detected.
1617 .BR \-y ", " \-\-syslog
1618 Cause all events to be reported through 'syslog'. The messages have
1619 facility of 'daemon' and varying priorities.
1622 .BR \-d ", " \-\-delay
1623 Give a delay in seconds.
1625 polls the md arrays and then waits this many seconds before polling
1626 again. The default is 60 seconds. Since 2.6.16, there is no need to
1627 reduce this as the kernel alerts
1629 immediately when there is any change.
1632 .BR \-r ", " \-\-increment
1633 Give a percentage increment.
1635 will generate RebuildNN events with the given percentage increment.
1638 .BR \-f ", " \-\-daemonise
1641 to run as a background daemon if it decides to monitor anything. This
1642 causes it to fork and run in the child, and to disconnect from the
1643 terminal. The process id of the child is written to stdout.
1646 which will only continue monitoring if a mail address or alert program
1647 is found in the config file.
1650 .BR \-i ", " \-\-pid\-file
1653 is running in daemon mode, write the pid of the daemon process to
1654 the specified file, instead of printing it on standard output.
1657 .BR \-1 ", " \-\-oneshot
1658 Check arrays only once. This will generate
1660 events and more significantly
1666 .B " mdadm \-\-monitor \-\-scan \-1"
1668 from a cron script will ensure regular notification of any degraded arrays.
1671 .BR \-t ", " \-\-test
1674 alert for every array found at startup. This alert gets mailed and
1675 passed to the alert program. This can be used for testing that alert
1676 message do get through successfully.
1680 This inhibits the functionality for moving spares between arrays.
1681 Only one monitoring process started with
1683 but without this flag is allowed, otherwise the two could interfere
1690 .B mdadm \-\-assemble
1691 .I md-device options-and-component-devices...
1694 .B mdadm \-\-assemble \-\-scan
1695 .I md-devices-and-options...
1698 .B mdadm \-\-assemble \-\-scan
1702 This usage assembles one or more RAID arrays from pre-existing components.
1703 For each array, mdadm needs to know the md device, the identity of the
1704 array, and a number of component-devices. These can be found in a number of ways.
1706 In the first usage example (without the
1708 the first device given is the md device.
1709 In the second usage example, all devices listed are treated as md
1710 devices and assembly is attempted.
1711 In the third (where no devices are listed) all md devices that are
1712 listed in the configuration file are assembled. If no arrays are
1713 described by the configuration file, then any arrays that
1714 can be found on unused devices will be assembled.
1716 If precisely one device is listed, but
1722 was given and identity information is extracted from the configuration file.
1724 The identity can be given with the
1730 option, will be taken from the md-device record in the config file, or
1731 will be taken from the super block of the first component-device
1732 listed on the command line.
1734 Devices can be given on the
1736 command line or in the config file. Only devices which have an md
1737 superblock which contains the right identity will be considered for
1740 The config file is only used if explicitly named with
1742 or requested with (a possibly implicit)
1747 .B /etc/mdadm/mdadm.conf
1752 is not given, then the config file will only be used to find the
1753 identity of md arrays.
1755 Normally the array will be started after it is assembled. However if
1757 is not given and not all expected drives were listed, then the array
1758 is not started (to guard against usage errors). To insist that the
1759 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1768 does not create any entries in
1772 It does record information in
1776 to choose the correct name.
1780 detects that udev is not configured, it will create the devices in
1784 In Linux kernels prior to version 2.6.28 there were two distinctly
1785 different types of md devices that could be created: one that could be
1786 partitioned using standard partitioning tools and one that could not.
1787 Since 2.6.28 that distinction is no longer relevant as both type of
1788 devices can be partitioned.
1790 will normally create the type that originally could not be partitioned
1791 as it has a well defined major number (9).
1793 Prior to 2.6.28, it is important that mdadm chooses the correct type
1794 of array device to use. This can be controlled with the
1796 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1797 to use a partitionable device rather than the default.
1799 In the no-udev case, the value given to
1801 can be suffixed by a number. This tells
1803 to create that number of partition devices rather than the default of 4.
1807 can also be given in the configuration file as a word starting
1809 on the ARRAY line for the relevant array.
1816 and no devices are listed,
1818 will first attempt to assemble all the arrays listed in the config
1821 If no arrays are listed in the config (other than those marked
1823 it will look through the available devices for possible arrays and
1824 will try to assemble anything that it finds. Arrays which are tagged
1825 as belonging to the given homehost will be assembled and started
1826 normally. Arrays which do not obviously belong to this host are given
1827 names that are expected not to conflict with anything local, and are
1828 started "read-auto" so that nothing is written to any device until the
1829 array is written to. i.e. automatic resync etc is delayed.
1833 finds a consistent set of devices that look like they should comprise
1834 an array, and if the superblock is tagged as belonging to the given
1835 home host, it will automatically choose a device name and try to
1836 assemble the array. If the array uses version-0.90 metadata, then the
1838 number as recorded in the superblock is used to create a name in
1842 If the array uses version-1 metadata, then the
1844 from the superblock is used to similarly create a name in
1846 (the name will have any 'host' prefix stripped first).
1848 This behaviour can be modified by the
1852 configuration file. This line can indicate that specific metadata
1853 type should, or should not, be automatically assembled. If an array
1854 is found which is not listed in
1856 and has a metadata format that is denied by the
1858 line, then it will not be assembled.
1861 line can also request that all arrays identified as being for this
1862 homehost should be assembled regardless of their metadata type.
1865 for further details.
1867 Note: Auto assembly cannot be used for assembling and activating some
1868 arrays which are undergoing reshape. In particular as the
1870 cannot be given, any reshape which requires a backup-file to continue
1871 cannot be started by auto assembly. An array which is growing to more
1872 devices and has passed the critical section can be assembled using
1883 .BI \-\-raid\-devices= Z
1887 This usage is similar to
1889 The difference is that it creates an array without a superblock. With
1890 these arrays there is no difference between initially creating the array and
1891 subsequently assembling the array, except that hopefully there is useful
1892 data there in the second case.
1894 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
1895 one of their synonyms. All devices must be listed and the array will
1896 be started once complete. It will often be appropriate to use
1897 .B \-\-assume\-clean
1898 with levels raid1 or raid10.
1909 .BI \-\-raid\-devices= Z
1913 This usage will initialise a new md array, associate some devices with
1914 it, and activate the array.
1916 The named device will normally not exist when
1917 .I "mdadm \-\-create"
1918 is run, but will be created by
1920 once the array becomes active.
1922 As devices are added, they are checked to see if they contain RAID
1923 superblocks or filesystems. They are also checked to see if the variance in
1924 device size exceeds 1%.
1926 If any discrepancy is found, the array will not automatically be run, though
1929 can override this caution.
1931 To create a "degraded" array in which some devices are missing, simply
1932 give the word "\fBmissing\fP"
1933 in place of a device name. This will cause
1935 to leave the corresponding slot in the array empty.
1936 For a RAID4 or RAID5 array at most one slot can be
1937 "\fBmissing\fP"; for a RAID6 array at most two slots.
1938 For a RAID1 array, only one real device needs to be given. All of the
1942 When creating a RAID5 array,
1944 will automatically create a degraded array with an extra spare drive.
1945 This is because building the spare into a degraded array is in general
1946 faster than resyncing the parity on a non-degraded, but not clean,
1947 array. This feature can be overridden with the
1951 When creating an array with version-1 metadata a name for the array is
1953 If this is not given with the
1957 will choose a name based on the last component of the name of the
1958 device being created. So if
1960 is being created, then the name
1965 is being created, then the name
1969 When creating a partition based array, using
1971 with version-1.x metadata, the partition type should be set to
1973 (non fs-data). This type selection allows for greater precision since
1974 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
1975 might create problems in the event of array recovery through a live cdrom.
1977 A new array will normally get a randomly assigned 128bit UUID which is
1978 very likely to be unique. If you have a specific need, you can choose
1979 a UUID for the array by giving the
1981 option. Be warned that creating two arrays with the same UUID is a
1982 recipe for disaster. Also, using
1984 when creating a v0.90 array will silently override any
1989 .\"option is given, it is not necessary to list any component-devices in this command.
1990 .\"They can be added later, before a
1994 .\"is given, the apparent size of the smallest drive given is used.
1996 If the array type supports a write-intent bitmap, and if the devices
1997 in the array exceed 100G is size, an internal write-intent bitmap
1998 will automatically be added unless some other option is explicitly
2001 option. In any case space for a bitmap will be reserved so that one
2002 can be added layer with
2003 .BR "\-\-grow \-\-bitmap=internal" .
2005 If the metadata type supports it (currently only 1.x metadata), space
2006 will be allocated to store a bad block list. This allows a modest
2007 number of bad blocks to be recorded, allowing the drive to remain in
2008 service while only partially functional.
2010 When creating an array within a
2013 can be given either the list of devices to use, or simply the name of
2014 the container. The former case gives control over which devices in
2015 the container will be used for the array. The latter case allows
2017 to automatically choose which devices to use based on how much spare
2020 The General Management options that are valid with
2025 insist on running the array even if some devices look like they might
2030 start the array readonly \(em not supported yet.
2037 .I options... devices...
2040 This usage will allow individual devices in an array to be failed,
2041 removed or added. It is possible to perform multiple operations with
2042 on command. For example:
2044 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2050 and will then remove it from the array and finally add it back
2051 in as a spare. However only one md array can be affected by a single
2054 When a device is added to an active array, mdadm checks to see if it
2055 has metadata on it which suggests that it was recently a member of the
2056 array. If it does, it tries to "re\-add" the device. If there have
2057 been no changes since the device was removed, or if the array has a
2058 write-intent bitmap which has recorded whatever changes there were,
2059 then the device will immediately become a full member of the array and
2060 those differences recorded in the bitmap will be resolved.
2070 MISC mode includes a number of distinct operations that
2071 operate on distinct devices. The operations are:
2074 The device is examined to see if it is
2075 (1) an active md array, or
2076 (2) a component of an md array.
2077 The information discovered is reported.
2081 The device should be an active md device.
2083 will display a detailed description of the array.
2087 will cause the output to be less detailed and the format to be
2088 suitable for inclusion in
2092 will normally be 0 unless
2094 failed to get useful information about the device(s); however, if the
2096 option is given, then the exit status will be:
2100 The array is functioning normally.
2103 The array has at least one failed device.
2106 The array has multiple failed devices such that it is unusable.
2109 There was an error while trying to get information about the device.
2113 .B \-\-detail\-platform
2114 Print detail of the platform's RAID capabilities (firmware / hardware
2115 topology). If the metadata is specified with
2119 then the return status will be:
2123 metadata successfully enumerated its platform components on this system
2126 metadata is platform independent
2129 metadata failed to find its platform components on this system
2133 .B \-\-update\-subarray=
2134 If the device is a container and the argument to \-\-update\-subarray
2135 specifies a subarray in the container, then attempt to update the given
2136 superblock field in the subarray. Similar to updating an array in
2137 "assemble" mode, the field to update is selected by
2141 option. Currently only
2147 option updates the subarray name in the metadata, it may not affect the
2148 device node name or the device node symlink until the subarray is
2149 re\-assembled. If updating
2151 would change the UUID of an active subarray this operation is blocked,
2152 and the command will end in an error.
2156 The device should be a component of an md array.
2158 will read the md superblock of the device and display the contents.
2163 is given, then multiple devices that are components of the one array
2164 are grouped together and reported in a single entry suitable
2170 without listing any devices will cause all devices listed in the
2171 config file to be examined.
2174 .BI \-\-dump= directory
2175 If the device contains RAID metadata, a file will be created in the
2177 and the metadata will be written to it. The file will be the same
2178 size as the device and have the metadata written in the file at the
2179 same locate that it exists in the device. However the file will be "sparse" so
2180 that only those blocks containing metadata will be allocated. The
2181 total space used will be small.
2183 The file name used in the
2185 will be the base name of the device. Further if any links appear in
2187 which point to the device, then hard links to the file will be created
2194 Multiple devices can be listed and their metadata will all be stored
2195 in the one directory.
2198 .BI \-\-restore= directory
2199 This is the reverse of
2202 will locate a file in the directory that has a name appropriate for
2203 the given device and will restore metadata from it. Names that match
2205 names are preferred, however if two of those refer to different files,
2207 will not choose between them but will abort the operation.
2209 If a file name is given instead of a
2213 will restore from that file to a single device, always provided the
2214 size of the file matches that of the device, and the file contains
2218 The devices should be active md arrays which will be deactivated, as
2219 long as they are not currently in use.
2223 This will fully activate a partially assembled md array.
2227 This will mark an active array as read-only, providing that it is
2228 not currently being used.
2234 array back to being read/write.
2238 For all operations except
2241 will cause the operation to be applied to all arrays listed in
2246 causes all devices listed in the config file to be examined.
2249 .BR \-b ", " \-\-brief
2250 Be less verbose. This is used with
2258 gives an intermediate level of verbosity.
2264 .B mdadm \-\-monitor
2265 .I options... devices...
2270 to periodically poll a number of md arrays and to report on any events
2273 will never exit once it decides that there are arrays to be checked,
2274 so it should normally be run in the background.
2276 As well as reporting events,
2278 may move a spare drive from one array to another if they are in the
2283 and if the destination array has a failed drive but no spares.
2285 If any devices are listed on the command line,
2287 will only monitor those devices. Otherwise all arrays listed in the
2288 configuration file will be monitored. Further, if
2290 is given, then any other md devices that appear in
2292 will also be monitored.
2294 The result of monitoring the arrays is the generation of events.
2295 These events are passed to a separate program (if specified) and may
2296 be mailed to a given E-mail address.
2298 When passing events to a program, the program is run once for each event,
2299 and is given 2 or 3 command-line arguments: the first is the
2300 name of the event (see below), the second is the name of the
2301 md device which is affected, and the third is the name of a related
2302 device if relevant (such as a component device that has failed).
2306 is given, then a program or an E-mail address must be specified on the
2307 command line or in the config file. If neither are available, then
2309 will not monitor anything.
2313 will continue monitoring as long as something was found to monitor. If
2314 no program or email is given, then each event is reported to
2317 The different events are:
2321 .B DeviceDisappeared
2322 An md array which previously was configured appears to no longer be
2323 configured. (syslog priority: Critical)
2327 was told to monitor an array which is RAID0 or Linear, then it will
2329 .B DeviceDisappeared
2330 with the extra information
2332 This is because RAID0 and Linear do not support the device-failed,
2333 hot-spare and resync operations which are monitored.
2337 An md array started reconstruction. (syslog priority: Warning)
2343 is a two-digit number (ie. 05, 48). This indicates that rebuild
2344 has passed that many percent of the total. The events are generated
2345 with fixed increment since 0. Increment size may be specified with
2346 a commandline option (default is 20). (syslog priority: Warning)
2350 An md array that was rebuilding, isn't any more, either because it
2351 finished normally or was aborted. (syslog priority: Warning)
2355 An active component device of an array has been marked as
2356 faulty. (syslog priority: Critical)
2360 A spare component device which was being rebuilt to replace a faulty
2361 device has failed. (syslog priority: Critical)
2365 A spare component device which was being rebuilt to replace a faulty
2366 device has been successfully rebuilt and has been made active.
2367 (syslog priority: Info)
2371 A new md array has been detected in the
2373 file. (syslog priority: Info)
2377 A newly noticed array appears to be degraded. This message is not
2380 notices a drive failure which causes degradation, but only when
2382 notices that an array is degraded when it first sees the array.
2383 (syslog priority: Critical)
2387 A spare drive has been moved from one array in a
2391 to another to allow a failed drive to be replaced.
2392 (syslog priority: Info)
2398 has been told, via the config file, that an array should have a certain
2399 number of spare devices, and
2401 detects that it has fewer than this number when it first sees the
2402 array, it will report a
2405 (syslog priority: Warning)
2409 An array was found at startup, and the
2412 (syslog priority: Info)
2422 cause Email to be sent. All events cause the program to be run.
2423 The program is run with two or three arguments: the event
2424 name, the array device and possibly a second device.
2426 Each event has an associated array device (e.g.
2428 and possibly a second device. For
2433 the second device is the relevant component device.
2436 the second device is the array that the spare was moved from.
2440 to move spares from one array to another, the different arrays need to
2441 be labeled with the same
2443 or the spares must be allowed to migrate through matching POLICY domains
2444 in the configuration file. The
2446 name can be any string; it is only necessary that different spare
2447 groups use different names.
2451 detects that an array in a spare group has fewer active
2452 devices than necessary for the complete array, and has no spare
2453 devices, it will look for another array in the same spare group that
2454 has a full complement of working drive and a spare. It will then
2455 attempt to remove the spare from the second drive and add it to the
2457 If the removal succeeds but the adding fails, then it is added back to
2460 If the spare group for a degraded array is not defined,
2462 will look at the rules of spare migration specified by POLICY lines in
2464 and then follow similar steps as above if a matching spare is found.
2467 The GROW mode is used for changing the size or shape of an active
2469 For this to work, the kernel must support the necessary change.
2470 Various types of growth are being added during 2.6 development.
2472 Currently the supported changes include
2474 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2476 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2479 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2481 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2482 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2484 add a write-intent bitmap to any array which supports these bitmaps, or
2485 remove a write-intent bitmap from such an array.
2488 Using GROW on containers is currently supported only for Intel's IMSM
2489 container format. The number of devices in a container can be
2490 increased - which affects all arrays in the container - or an array
2491 in a container can be converted between levels where those levels are
2492 supported by the container, and the conversion is on of those listed
2493 above. Resizing arrays in an IMSM container with
2495 is not yet supported.
2497 Grow functionality (e.g. expand a number of raid devices) for Intel's
2498 IMSM container format has an experimental status. It is guarded by the
2499 .B MDADM_EXPERIMENTAL
2500 environment variable which must be set to '1' for a GROW command to
2502 This is for the following reasons:
2505 Intel's native IMSM check-pointing is not fully tested yet.
2506 This can causes IMSM incompatibility during the grow process: an array
2507 which is growing cannot roam between Microsoft Windows(R) and Linux
2511 Interrupting a grow operation is not recommended, because it
2512 has not been fully tested for Intel's IMSM container format yet.
2515 Note: Intel's native checkpointing doesn't use
2517 option and it is transparent for assembly feature.
2520 Normally when an array is built the "size" is taken from the smallest
2521 of the drives. If all the small drives in an arrays are, one at a
2522 time, removed and replaced with larger drives, then you could have an
2523 array of large drives with only a small amount used. In this
2524 situation, changing the "size" with "GROW" mode will allow the extra
2525 space to start being used. If the size is increased in this way, a
2526 "resync" process will start to make sure the new parts of the array
2529 Note that when an array changes size, any filesystem that may be
2530 stored in the array will not automatically grow or shrink to use or
2531 vacate the space. The
2532 filesystem will need to be explicitly told to use the extra space
2533 after growing, or to reduce its size
2535 to shrinking the array.
2537 Also the size of an array cannot be changed while it has an active
2538 bitmap. If an array has a bitmap, it must be removed before the size
2539 can be changed. Once the change is complete a new bitmap can be created.
2541 .SS RAID\-DEVICES CHANGES
2543 A RAID1 array can work with any number of devices from 1 upwards
2544 (though 1 is not very useful). There may be times which you want to
2545 increase or decrease the number of active devices. Note that this is
2546 different to hot-add or hot-remove which changes the number of
2549 When reducing the number of devices in a RAID1 array, the slots which
2550 are to be removed from the array must already be vacant. That is, the
2551 devices which were in those slots must be failed and removed.
2553 When the number of devices is increased, any hot spares that are
2554 present will be activated immediately.
2556 Changing the number of active devices in a RAID5 or RAID6 is much more
2557 effort. Every block in the array will need to be read and written
2558 back to a new location. From 2.6.17, the Linux Kernel is able to
2559 increase the number of devices in a RAID5 safely, including restarting
2560 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2561 increase or decrease the number of devices in a RAID5 or RAID6.
2563 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2566 uses this functionality and the ability to add
2567 devices to a RAID4 to allow devices to be added to a RAID0. When
2568 requested to do this,
2570 will convert the RAID0 to a RAID4, add the necessary disks and make
2571 the reshape happen, and then convert the RAID4 back to RAID0.
2573 When decreasing the number of devices, the size of the array will also
2574 decrease. If there was data in the array, it could get destroyed and
2575 this is not reversible, so you should firstly shrink the filesystem on
2576 the array to fit within the new size. To help prevent accidents,
2578 requires that the size of the array be decreased first with
2579 .BR "mdadm --grow --array-size" .
2580 This is a reversible change which simply makes the end of the array
2581 inaccessible. The integrity of any data can then be checked before
2582 the non-reversible reduction in the number of devices is request.
2584 When relocating the first few stripes on a RAID5 or RAID6, it is not
2585 possible to keep the data on disk completely consistent and
2586 crash-proof. To provide the required safety, mdadm disables writes to
2587 the array while this "critical section" is reshaped, and takes a
2588 backup of the data that is in that section. For grows, this backup may be
2589 stored in any spare devices that the array has, however it can also be
2590 stored in a separate file specified with the
2592 option, and is required to be specified for shrinks, RAID level
2593 changes and layout changes. If this option is used, and the system
2594 does crash during the critical period, the same file must be passed to
2596 to restore the backup and reassemble the array. When shrinking rather
2597 than growing the array, the reshape is done from the end towards the
2598 beginning, so the "critical section" is at the end of the reshape.
2602 Changing the RAID level of any array happens instantaneously. However
2603 in the RAID5 to RAID6 case this requires a non-standard layout of the
2604 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2605 required before the change can be accomplished. So while the level
2606 change is instant, the accompanying layout change can take quite a
2609 is required. If the array is not simultaneously being grown or
2610 shrunk, so that the array size will remain the same - for example,
2611 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2612 be used not just for a "cricital section" but throughout the reshape
2613 operation, as described below under LAYOUT CHANGES.
2615 .SS CHUNK-SIZE AND LAYOUT CHANGES
2617 Changing the chunk-size of layout without also changing the number of
2618 devices as the same time will involve re-writing all blocks in-place.
2619 To ensure against data loss in the case of a crash, a
2621 must be provided for these changes. Small sections of the array will
2622 be copied to the backup file while they are being rearranged. This
2623 means that all the data is copied twice, once to the backup and once
2624 to the new layout on the array, so this type of reshape will go very
2627 If the reshape is interrupted for any reason, this backup file must be
2629 .B "mdadm --assemble"
2630 so the array can be reassembled. Consequently the file cannot be
2631 stored on the device being reshaped.
2636 A write-intent bitmap can be added to, or removed from, an active
2637 array. Either internal bitmaps, or bitmaps stored in a separate file,
2638 can be added. Note that if you add a bitmap stored in a file which is
2639 in a filesystem that is on the RAID array being affected, the system
2640 will deadlock. The bitmap must be on a separate filesystem.
2642 .SH INCREMENTAL MODE
2646 .B mdadm \-\-incremental
2652 .B mdadm \-\-incremental \-\-fail
2656 .B mdadm \-\-incremental \-\-rebuild\-map
2659 .B mdadm \-\-incremental \-\-run \-\-scan
2662 This mode is designed to be used in conjunction with a device
2663 discovery system. As devices are found in a system, they can be
2665 .B "mdadm \-\-incremental"
2666 to be conditionally added to an appropriate array.
2668 Conversely, it can also be used with the
2670 flag to do just the opposite and find whatever array a particular device
2671 is part of and remove the device from that array.
2673 If the device passed is a
2675 device created by a previous call to
2677 then rather than trying to add that device to an array, all the arrays
2678 described by the metadata of the container will be started.
2681 performs a number of tests to determine if the device is part of an
2682 array, and which array it should be part of. If an appropriate array
2683 is found, or can be created,
2685 adds the device to the array and conditionally starts the array.
2689 will normally only add devices to an array which were previously working
2690 (active or spare) parts of that array. The support for automatic
2691 inclusion of a new drive as a spare in some array requires
2692 a configuration through POLICY in config file.
2696 makes are as follow:
2698 Is the device permitted by
2700 That is, is it listed in a
2702 line in that file. If
2704 is absent then the default it to allow any device. Similar if
2706 contains the special word
2708 then any device is allowed. Otherwise the device name given to
2710 must match one of the names or patterns in a
2715 Does the device have a valid md superblock? If a specific metadata
2716 version is requested with
2720 then only that style of metadata is accepted, otherwise
2722 finds any known version of metadata. If no
2724 metadata is found, the device may be still added to an array
2725 as a spare if POLICY allows.
2729 Does the metadata match an expected array?
2730 The metadata can match in two ways. Either there is an array listed
2733 which identifies the array (either by UUID, by name, by device list,
2734 or by minor-number), or the array was created with a
2740 or on the command line.
2743 is not able to positively identify the array as belonging to the
2744 current host, the device will be rejected.
2749 keeps a list of arrays that it has partially assembled in
2751 If no array exists which matches
2752 the metadata on the new device,
2754 must choose a device name and unit number. It does this based on any
2757 or any name information stored in the metadata. If this name
2758 suggests a unit number, that number will be used, otherwise a free
2759 unit number will be chosen. Normally
2761 will prefer to create a partitionable array, however if the
2765 suggests that a non-partitionable array is preferred, that will be
2768 If the array is not found in the config file and its metadata does not
2769 identify it as belonging to the "homehost", then
2771 will choose a name for the array which is certain not to conflict with
2772 any array which does belong to this host. It does this be adding an
2773 underscore and a small number to the name preferred by the metadata.
2775 Once an appropriate array is found or created and the device is added,
2777 must decide if the array is ready to be started. It will
2778 normally compare the number of available (non-spare) devices to the
2779 number of devices that the metadata suggests need to be active. If
2780 there are at least that many, the array will be started. This means
2781 that if any devices are missing the array will not be restarted.
2787 in which case the array will be run as soon as there are enough
2788 devices present for the data to be accessible. For a RAID1, that
2789 means one device will start the array. For a clean RAID5, the array
2790 will be started as soon as all but one drive is present.
2792 Note that neither of these approaches is really ideal. If it can
2793 be known that all device discovery has completed, then
2797 can be run which will try to start all arrays that are being
2798 incrementally assembled. They are started in "read-auto" mode in
2799 which they are read-only until the first write request. This means
2800 that no metadata updates are made and no attempt at resync or recovery
2801 happens. Further devices that are found before the first write can
2802 still be added safely.
2805 This section describes environment variables that affect how mdadm
2810 Setting this value to 1 will prevent mdadm from automatically launching
2811 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2817 does not create any device nodes in /dev, but leaves that task to
2821 appears not to be configured, or if this environment variable is set
2824 will create and devices that are needed.
2828 A key value of IMSM metadata is that it allows interoperability with
2829 boot ROMs on Intel platforms, and with other major operating systems.
2832 will only allow an IMSM array to be created or modified if detects
2833 that it is running on an Intel platform which supports IMSM, and
2834 supports the particular configuration of IMSM that is being requested
2835 (some functionality requires newer OROM support).
2837 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
2838 environment. This can be useful for testing or for disaster
2839 recovery. You should be aware that interoperability may be
2840 compromised by setting this value.
2843 .B " mdadm \-\-query /dev/name-of-device"
2845 This will find out if a given device is a RAID array, or is part of
2846 one, and will provide brief information about the device.
2848 .B " mdadm \-\-assemble \-\-scan"
2850 This will assemble and start all arrays listed in the standard config
2851 file. This command will typically go in a system startup file.
2853 .B " mdadm \-\-stop \-\-scan"
2855 This will shut down all arrays that can be shut down (i.e. are not
2856 currently in use). This will typically go in a system shutdown script.
2858 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
2860 If (and only if) there is an Email address or program given in the
2861 standard config file, then
2862 monitor the status of all arrays listed in that file by
2863 polling them ever 2 minutes.
2865 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
2867 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2870 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
2872 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
2874 This will create a prototype config file that describes currently
2875 active arrays that are known to be made from partitions of IDE or SCSI drives.
2876 This file should be reviewed before being used as it may
2877 contain unwanted detail.
2879 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
2881 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
2883 This will find arrays which could be assembled from existing IDE and
2884 SCSI whole drives (not partitions), and store the information in the
2885 format of a config file.
2886 This file is very likely to contain unwanted detail, particularly
2889 entries. It should be reviewed and edited before being used as an
2892 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
2894 .B " mdadm \-Ebsc partitions"
2896 Create a list of devices by reading
2897 .BR /proc/partitions ,
2898 scan these for RAID superblocks, and printout a brief listing of all
2901 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
2903 Scan all partitions and devices listed in
2904 .BR /proc/partitions
2907 out of all such devices with a RAID superblock with a minor number of 0.
2909 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
2911 If config file contains a mail address or alert program, run mdadm in
2912 the background in monitor mode monitoring all md devices. Also write
2913 pid of mdadm daemon to
2914 .BR /run/mdadm/mon.pid .
2916 .B " mdadm \-Iq /dev/somedevice"
2918 Try to incorporate newly discovered device into some array as
2921 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
2923 Rebuild the array map from any current arrays, and then start any that
2926 .B " mdadm /dev/md4 --fail detached --remove detached"
2928 Any devices which are components of /dev/md4 will be marked as faulty
2929 and then remove from the array.
2931 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
2935 which is currently a RAID5 array will be converted to RAID6. There
2936 should normally already be a spare drive attached to the array as a
2937 RAID6 needs one more drive than a matching RAID5.
2939 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
2941 Create a DDF array over 6 devices.
2943 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
2945 Create a RAID5 array over any 3 devices in the given DDF set. Use
2946 only 30 gigabytes of each device.
2948 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
2950 Assemble a pre-exist ddf array.
2952 .B " mdadm -I /dev/md/ddf1"
2954 Assemble all arrays contained in the ddf array, assigning names as
2957 .B " mdadm \-\-create \-\-help"
2959 Provide help about the Create mode.
2961 .B " mdadm \-\-config \-\-help"
2963 Provide help about the format of the config file.
2965 .B " mdadm \-\-help"
2967 Provide general help.
2977 lists all active md devices with information about them.
2979 uses this to find arrays when
2981 is given in Misc mode, and to monitor array reconstruction
2986 The config file lists which devices may be scanned to see if
2987 they contain MD super block, and gives identifying information
2988 (e.g. UUID) about known MD arrays. See
2992 .SS /etc/mdadm.conf.d
2994 A directory containing configuration files which are read in lexical
3000 mode is used, this file gets a list of arrays currently being created.
3005 understand two sorts of names for array devices.
3007 The first is the so-called 'standard' format name, which matches the
3008 names used by the kernel and which appear in
3011 The second sort can be freely chosen, but must reside in
3013 When giving a device name to
3015 to create or assemble an array, either full path name such as
3019 can be given, or just the suffix of the second sort of name, such as
3025 chooses device names during auto-assembly or incremental assembly, it
3026 will sometimes add a small sequence number to the end of the name to
3027 avoid conflicted between multiple arrays that have the same name. If
3029 can reasonably determine that the array really is meant for this host,
3030 either by a hostname in the metadata, or by the presence of the array
3033 then it will leave off the suffix if possible.
3034 Also if the homehost is specified as
3037 will only use a suffix if a different array of the same name already
3038 exists or is listed in the config file.
3040 The standard names for non-partitioned arrays (the only sort of md
3041 array available in 2.4 and earlier) are of the form
3045 where NN is a number.
3046 The standard names for partitionable arrays (as available from 2.6
3047 onwards) are of the form:
3051 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3053 From kernel version 2.6.28 the "non-partitioned array" can actually
3054 be partitioned. So the "md_d\fBNN\fP"
3055 names are no longer needed, and
3056 partitions such as "/dev/md\fBNN\fPp\fBXX\fp"
3059 From kernel version 2.6.29 standard names can be non-numeric following
3066 is any string. These names are supported by
3068 since version 3.3 provided they are enabled in
3073 was previously known as
3077 For further information on mdadm usage, MD and the various levels of
3080 .B http://raid.wiki.kernel.org/
3082 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3084 The latest version of
3086 should always be available from
3088 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob