2 .TH MDADM 8 "" v2.0-devel-3
4 mdadm \- manage MD devices
10 .BI mdadm " [mode] <raiddevice> [options] <component-devices>"
13 RAID devices are virtual devices created from two or more
14 real block devices. This allows multiple devices (typically disk
15 drives or partitions there-of) to be combined into a single device to
16 hold (for example) a single filesystem.
17 Some RAID levels include redundancy and so can survive some degree of
20 Linux Software RAID devices are implemented through the md (Multiple
21 Devices) device driver.
23 Currently, Linux supports
37 .B MULTIPATH is not a Software RAID mechanism, but does involve
40 each device is a path to one common physical storage device.
42 .B FAULTY is also no true RAID, and it only involves one device. It
43 provides a layer over a true device that can be used to inject faults.
46 is a program that can be used to create, manage, and monitor
48 such it provides a similar set of functionality to the
51 The key differences between
58 is a single program and not a collection of programs.
61 can perform (almost) all of its functions without having a
62 configuration file and does not use one by default. Also
64 helps with management of the configuration
68 can provide information about your arrays (through Query, Detail, and Examine)
78 configuration file, at all. It has a different configuration file
79 with a different format and an different purpose.
82 mdadm has 7 major modes of operation:
85 Assemble the parts of a previously created
86 array into an active array. Components can be explicitly given
87 or can be searched for.
89 checks that the components
90 do form a bona fide array, and can, on request, fiddle superblock
91 information so as to assemble a faulty array.
95 Build an array without per-device superblocks.
99 Create a new array with per-device superblocks.
101 '''in several step create-add-add-run or it can all happen with one command.
105 This is for doing things to specific components of an array such as
106 adding new spares and removing faulty devices.
110 This mode allows operations on independent devices such as examine MD
111 superblocks, erasing old superblocks and stopping active arrays.
114 .B "Follow or Monitor"
115 Monitor one or more md devices and act on any state changes. This is
116 only meaningful for raid1, 4, 5, 6 or multipath arrays as
117 only these have interesting state. raid0 or linear never have
118 missing, spare, or failed drives, so there is nothing to monitor.
122 Grow (or shrink) an array, or otherwise reshape it in some way.
123 Currently supported growth options including changing the active size
124 of componenet devices in RAID level 1/4/5/6 and changing the number of
125 active devices in RAID1.
129 Available options are:
132 .BR -A ", " --assemble
133 Assemble a pre-existing array.
137 Build a legacy array without superblocks.
145 Examine a device to see
146 (1) if it is an md device and (2) if it is a component of an md
148 Information about what is discovered is presented.
152 Print detail of one or more md devices.
155 .BR -E ", " --examine
156 Print content of md superblock on device(s).
159 .BR -F ", " --follow ", " --monitor
166 Change the size or shape of an active array.
169 .BR -X ", " --examine-bitmap
170 Report information about a bitmap file.
174 Display help message or, after above option, mode specific help
179 Display more detailed help about command line parsing and some commonly
183 .BR -V ", " --version
184 Print version information for mdadm.
187 .BR -v ", " --verbose
188 Be more verbose about what is happening. This can be used twice to be
190 This currently only affects
193 .BR "--examine --scan" .
197 Avoid printing purely informative messages. With this,
199 will be silent unless there is something really important to report.
203 Be less verbose. This is used with
211 gives an intermediate level of verbosity.
214 .BR -W ", " --write-mostly
215 subsequent devices lists in a
220 command will be flagged as 'write-mostly'. This is valid for RAID1
221 only and means that the 'md' driver will avoid reading from these
222 devices if at all possible. This can be useful if mirroring over a
226 .BR -b ", " --bitmap=
227 Give the name of a bitmap file to use with this array. Can be used
228 with --create (file should not exist), --assemble (file should
229 exist), of --grow (file should not exist).
233 can be used to indicate that the bitmap should be stored in the array,
234 near the superblock. There is a limited amount of space for such
235 bitmaps, but it is often sufficient.
239 can be given when used with --grow to remove a bitmap.
243 Set the Chunksize of the bitmap. Each bit corresponds to that many
244 Kilobytes of storage. Default is 4.
248 Specify that write-behind mode should be enabled (valid for RAID1
249 only). If an argument is specified, it will set the maximum number
250 of outstanding writes allowed. The default value is 256.
251 A write-intent bitmap is required in order to use write-behind
252 mode, and write-behind is only attempted on drives marked as
258 Be more forceful about certain operations. See the various modes of
259 the exact meaning of this option in different contexts.
262 .BR -c ", " --config=
263 Specify the config file. Default is
264 .BR /etc/mdadm.conf .
265 If the config file given is
267 then nothing will be read, but
269 will act as though the config file contained exactly
270 .B "DEVICE partitions"
273 to find a list of devices to scan.
276 is given for the config file, then
278 will act as though the config file were empty.
284 for missing information.
285 In general, this option gives
287 permission to get any missing information, like component devices,
288 array devices, array identities, and alert destination from the
290 .BR /etc/mdadm.conf .
291 One exception is MISC mode when using
297 says to get a list of array devices from
301 .B -e ", " --metadata=
302 Declare the style of superblock (raid metadata) to be used. The
303 default is 0.90 for --create, and to guess for other operations.
307 .IP "0, 0.90, default"
308 Use the original 0.90 format superblock. This format limits arrays to
309 28 componenet devices and limits component devices of levels 1 and
310 greater to 2 terabytes.
311 .IP "1, 1.0, 1.1, 1.2"
312 Use the new version-1 format superblock. This has few restrictions.
313 The different subversion store the superblock at different locations
314 on the device, either at the end (for 1.0), at the start (for 1.1) or
315 4K from the start (for 1.2).
318 .SH For create or build:
322 Specify chunk size of kibibytes. The default is 64.
326 Specify rounding factor for linear array (==chunk size)
330 Set raid level. When used with
332 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
333 raid5, 5, raid6, 6, multipath, mp, fautly. Obviously some of these are synonymous.
337 only linear, raid0, 0, stripe are valid.
340 .BR -p ", " --parity=
341 Set raid5 parity algorithm. Options are:
346 la, ra, ls, rs. The default is left-symmetric.
348 This option is also used to set the failure mode for
366 Each mode can be followed by a number which is used as a period
367 between fault generation. Without a number, the fault is generated
368 once on the first relevant request. With a number, the fault will be
369 generated after that many request, and will continue to be generated
370 every time the period elapses.
372 Multiple failure modes can be current simultaneously by using the
373 "--grow" option to set subsequent failure modes.
375 "clear" or "none" will remove any pending or periodic failure modes,
376 and "flush" will clear any persistant faults.
378 To set the parity with "--grow", the level of the array ("faulty")
379 must be specified before the fault mode is specified.
386 .BR -b ", " --bitmap=
387 Specify a file to store a write-intent bitmap in. The file should not
388 exist unless --force is also given. The same file should be provided
389 when assembling the array.
393 Specifty the chunksize for the bitmap.
396 .BR -n ", " --raid-devices=
397 Specify the number of active devices in the array. This, plus the
398 number of spare devices (see below) must equal the number of
400 (including "\fBmissing\fP" devices)
401 that are listed on the command line for
403 Setting a value of 1 is probably
404 a mistake and so requires that
406 be specified first. A value of 1 will then be allowed for linear,
407 multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
409 This number can only be changed using
411 for RAID1 arrays, and only on kernels which provide necessary support.
414 .BR -x ", " --spare-devices=
415 Specify the number of spare (eXtra) devices in the initial array.
416 Spares can also be added
417 and removed later. The number of component devices listed
418 on the command line must equal the number of raid devices plus the
419 number of spare devices.
424 Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6.
425 This must be a multiple of the chunk size, and must leave about 128Kb
426 of space at the end of the drive for the RAID superblock.
427 If this is not specified
428 (as it normally is not) the smallest drive (or partition) sets the
429 size, though if there is a variance among the drives of greater than 1%, a warning is
432 This value can be set with
434 for RAID level 1/4/5/6. If the array was created with a size smaller
435 than the currently active drives, the extra space can be accessed
438 The size can be given as
440 which means to choose the largest size that fits all on all current drives.
446 that the array pre-existed and is known to be clean. This is only
447 really useful for Building RAID1 array. Only use this if you really
448 know what you are doing. This is currently only supported for --build.
454 for the array. This is currently only effective when creating an
455 array with a version-1 superblock. The name is a simple textual
456 string that can be used to identify array components when assembling.
462 run the array, even if some of the components
463 appear to be active in another array or filesystem. Normally
465 will ask for confirmation before including such components in an
466 array. This option causes that question to be suppressed.
472 accept the geometry and layout specified without question. Normally
474 will not allow creation of an array with only one device, and will try
475 to create a raid5 array with one missing drive (as this makes the
476 initial resync work faster). With
479 will not try to be so clever.
482 .BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}"
483 Instruct mdadm to create the device file if needed, possibly allocating
484 an unused minor number. "md" causes a non-partitionable array
485 to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
486 later) to be used. "yes" requires the named md device to have a
487 'standard' format, and the type and minor number will be determined
488 from this. See DEVICE NAMES below.
490 The argumentment can also come immediately after
495 is also given, then any
497 entries in the config file will over-ride the
499 instruction given on the command line.
501 For partitionable arrays,
503 will create the device file for the whole array and for the first 4
504 partitions. A different number of partitions can be specified at the
505 end of this option (e.g.
507 If the device name ends with a digit, the partition names add a'p',
508 and a number, e.g. "/dev/home1p3". If there is no
509 trailing digit, then the partition names just have a number added,
510 e.g. "/dev/scratch3".
512 If the md device name is in a 'standard' format as described in DEVICE
513 NAMES, then it will be created, if necessary, with the appropriate
514 number based on that name. If the device name is not in one of these
515 formats, then a unused minor number will be allocted. The minor
516 number will be considered unused if there is no active array for that
517 number, and there is no entry in /dev for that number and with a
524 uuid of array to assemble. Devices which don't have this uuid are
528 .BR -m ", " --super-minor=
529 Minor number of device that array was created for. Devices which
530 don't have this minor number are excluded. If you create an array as
531 /dev/md1, then all superblocks will contain the minor number 1, even if
532 the array is later assembled as /dev/md2.
534 Giving the literal word "dev" for
538 to use the minor number of the md device that is being assembled.
542 will look for super blocks with a minor number of 0.
546 Specify the name of the array to assemble. This must be the name
547 that was specified when creating the array.
551 Assemble the array even if some superblocks appear out-of-date
555 Attempt to start the array even if fewer drives were given than are
556 needed for a full array. Normally if not all drives are found and
558 is not used, then the array will be assembled but not started.
561 an attempt will be made to start it anyway.
564 .BR -a ", " "--auto{=no,yes,md,mdp,part}"
565 See this option under Create and Build options.
568 .BR -b ", " --bitmap=
569 Specify the bitmap file that was given when the array was created.
572 .BR -U ", " --update=
573 Update the superblock on each device while assembling the array. The
574 argument given to this flag can be one of
584 option will adjust the superblock of an array what was created on a Sparc
585 machine running a patched 2.2 Linux kernel. This kernel got the
586 alignment of part of the superblock wrong. You can use the
587 .B "--examine --sparc2.2"
590 to see what effect this would have.
594 option will update the
596 field on each superblock to match the minor number of the array being
597 assembled. This is not needed on 2.6 and later kernels as they make
598 this adjustment automatically.
602 option will cause the array to be marked
604 meaning that any redundancy in the array (e.g. parity for raid5,
605 copies for raid1) may be incorrect. This will cause the raid system
606 to perform a "resync" pass to make sure that all redundant information
611 option allows arrays to be moved between machines with different
613 When assembling such an array for the first time after a move, giving
614 .B "--update=byteorder"
617 to expect superblocks to have their byteorder reversed, and will
618 correct that order before assembling the array. This is only valid
619 with original (Verion 0.90) superblocks.
623 option will correct the summaries in the superblock. That is the
624 counts of total, working, active, failed, and spare devices.
631 hotadd listed devices.
635 Listed devices are assumed to have recently been part of the array,
636 and they are re-added. This is only different from --add when a
637 write-intent bitmap is present. It causes only those parts of the
638 device that have changed since the device was removed from the array
641 This flag is only needed with arrays that are built without a
642 superblock (i.e. --build, not --create). For array with a superblock,
644 checks if a superblock is present and automatically determines if a
645 re-add is appropriate.
649 remove listed devices. They must not be active. i.e. they should
650 be failed or spare devices.
654 mark listed devices as faulty.
660 .SH For Examine mode:
664 In an array was created on a 2.2 Linux kernel patched with RAID
665 support, the superblock will have been created incorrectly, or at
666 least incompatibly with 2.4 and later kernels. Using the
670 will fix the superblock before displaying it. If this appears to do
671 the right thing, then the array can be successfully assembled using
672 .BR "--assemble --update=sparc2.2" .
678 start a partially built array.
682 deactivate array, releasing all resources.
685 .BR -o ", " --readonly
686 mark array as readonly.
689 .BR -w ", " --readwrite
690 mark array as readwrite.
694 If the device contains a valid md superblock, the block is
695 over-written with zeros. With
697 the block where the superblock would be is over-written even if it
698 doesn't appear to be valid.
706 is set to reflect the status of the device.
708 .SH For Monitor mode:
711 Give a mail address to send alerts to.
714 .BR -p ", " --program ", " --alert
715 Give a program to be run whenever an event is detected.
719 Give a delay in seconds.
721 polls the md arrays and then waits this many seconds before polling
722 again. The default is 60 seconds.
725 .BR -f ", " --daemonise
728 to run as a background daemon if it decides to monitor anything. This
729 causes it to fork and run in the child, and to disconnect form the
730 terminal. The process id of the child is written to stdout.
733 which will only continue monitoring if a mail address or alert program
734 is found in the config file.
737 .BR -i ", " --pid-file
740 is running in daemon mode, write the pid of the daemon process to
741 the specified file, instead of printing it on standard output.
744 .BR -1 ", " --oneshot
745 Check arrays only once. This will generate
747 events and more significantly
751 .B " mdadm --monitor --scan -1"
753 from a cron script will ensure regular notification of any degraded arrays.
759 alert for every array found at startup. This alert gets mailed and
760 passed to the alert program. This can be used for testing that alert
761 message to get through successfully.
768 .I md-device options-and-component-devices...
771 .B mdadm --assemble --scan
772 .I md-devices-and-options...
775 .B mdadm --assemble --scan
779 This usage assembles one or more raid arrays from pre-existing components.
780 For each array, mdadm needs to know the md device, the identity of the
781 array, and a number of component-devices. These can be found in a number of ways.
783 In the first usage example (without the
785 the first device given is the md device.
786 In the second usage example, all devices listed are treated as md
787 devices and assembly is attempted.
788 In the third (where no devices are listed) all md devices that are
789 listed in the configuration file are assembled.
791 If precisely one device is listed, but
797 was given and identify information is extracted from the configuration file.
799 The identity can be given with the
803 option, can be found in the config file, or will be taken from the
804 super block on the first component-device listed on the command line.
806 Devices can be given on the
808 command line or in the config file. Only devices which have an md
809 superblock which contains the right identity will be considered for
812 The config file is only used if explicitly named with
814 or requested with (a possibly implicit)
822 is not given, then the config file will only be used to find the
823 identity of md arrays.
825 Normally the array will be started after it is assembled. However if
827 is not given and insufficient drives were listed to start a complete
828 (non-degraded) array, then the array is not started (to guard against
829 usage errors). To insist that the array be started in this case (as
830 may work for RAID1, 4, 5 or 6), give the
836 option is given, either on the command line (--auto) or in the
837 configuration file (e.g. auto=part), then
839 will create the md device if necessary or will re-create it if it
840 doesn't look usable as it is.
842 This can be useful for handling partitioned devices (which don't have
843 a stable device number - it can change after a reboot) and when using
844 "udev" to manage your
846 tree (udev cannot handle md devices because of the unusual device
847 initialisation conventions).
849 If the option to "auto" is "mdp" or "part" or (on the command line
850 only) "p", then mdadm will create a partitionable array, using the
851 first free one that is not inuse, and does not already have an entry
852 in /dev (apart from numeric /dev/md* entries).
854 If the option to "auto" is "yes" or "md" or (on the command line)
855 nothing, then mdadm will create a traditional, non-partitionable md
858 It is expected that the "auto" functionality will be used to create
859 device entries with meaningful names such as "/dev/md/home" or
860 "/dev/md/root", rather than names based on the numerical array number.
862 When using this option to create a partitionable array, the device
863 files for the first 4 partitions are also created. If a different
864 number is required it can be simply appended to the auto option.
865 e.g. "auto=part8". Partition names are created by appending a digit
866 string to the device name, with an intervening "_p" if the device name
871 option is also available in Build and Create modes. As those modes do
872 not use a config file, the "auto=" config option does not apply to
883 .BI --raid-devices= Z
887 This usage is similar to
889 The difference is that it creates a legacy array without a superblock. With
890 these arrays there is no difference between initially creating the array and
891 subsequently assembling the array, except that hopefully there is useful
892 data there in the second case.
894 The level may only be 0, raid0, or linear. All devices must be listed
895 and the array will be started once complete.
906 .BI --raid-devices= Z
910 This usage will initialise a new md array, associate some devices with
911 it, and activate the array.
915 option is given (as described in more detail in the section on
916 Assemble mode), then the md device will be created with a suitable
917 device number if necessary.
919 As devices are added, they are checked to see if they contain raid
920 superblocks or filesystems. They are also checked to see if the variance in
921 device size exceeds 1%.
923 If any discrepancy is found, the array will not automatically be run, though
926 can override this caution.
928 To create a "degraded" array in which some devices are missing, simply
929 give the word "\fBmissing\fP"
930 in place of a device name. This will cause
932 to leave the corresponding slot in the array empty.
933 For a RAID4 or RAID5 array at most one slot can be
934 "\fBmissing\fP"; for a RAID6 array at most two slots.
935 For a RAID1 array, only one real device needs to be given. All of the
939 When creating a RAID5 array,
941 will automatically create a degraded array with an extra spare drive.
942 This is because building the spare into a degraded array is in general faster than resyncing
943 the parity on a non-degraded, but not clean, array. This feature can
944 be over-ridden with the
950 '''option is given, it is not necessary to list any component-devices in this command.
951 '''They can be added later, before a
955 '''is given, the apparent size of the smallest drive given is used.
957 The General Management options that are valid with --create are:
960 insist on running the array even if some devices look like they might
965 start the array readonly - not supported yet.
972 .I options... devices...
975 This usage will allow individual devices in an array to be failed,
976 removed or added. It is possible to perform multiple operations with
977 on command. For example:
979 .B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1"
985 and will then remove it from the array and finally add it back
986 in as a spare. However only one md array can be affected by a single
997 MISC mode includes a number of distinct operations that
998 operate on distinct devices. The operations are:
1001 The device is examined to see if it is
1002 (1) an active md array, or
1003 (2) a component of an md array.
1004 The information discovered is reported.
1008 The device should be an active md device.
1010 will display a detailed description of the array.
1014 will cause the output to be less detailed and the format to be
1015 suitable for inclusion in
1016 .BR /etc/mdadm.conf .
1019 will normally be 0 unless
1021 failed to get useful information about the device(s). However if the
1023 option is given, then the exit status will be:
1027 The array is functioning normally.
1030 The array has at least one failed device.
1033 The array has multiple failed devices and hence is unusable (raid4 or
1037 There was an error while trying to get information about the device.
1042 The device should be a component of an md array.
1044 will read the md superblock of the device and display the contents.
1049 then multiple devices that are components of the one array
1050 are grouped together and reported in a single entry suitable
1052 .BR /etc/mdadm.conf .
1056 without listing any devices will cause all devices listed in the
1057 config file to be examined.
1061 The devices should be active md arrays which will be deactivated, as
1062 long as they are not currently in use.
1066 This will fully activate a partially assembled md array.
1070 This will mark an active array as read-only, providing that it is
1071 not currently being used.
1077 array back to being read/write.
1081 For all operations except
1084 will cause the operation to be applied to all arrays listed in
1089 causes all devices listed in the config file to be examined.
1097 .I options... devices...
1102 to periodically poll a number of md arrays and to report on any events
1105 will never exit once it decides that there are arrays to be checked,
1106 so it should normally be run in the background.
1108 As well as reporting events,
1110 may move a spare drive from one array to another if they are in the
1113 and if the destination array has a failed drive but not spares.
1115 If any devices are listed on the command line,
1117 will only monitor those devices. Otherwise all arrays listed in the
1118 configuration file will be monitored. Further, if
1120 is given, then any other md devices that appear in
1122 will also be monitored.
1124 The result of monitoring the arrays is the generation of events.
1125 These events are passed to a separate program (if specified) and may
1126 be mailed to a given E-mail address.
1128 When passing event to program, the program is run once for each event
1129 and is given 2 or 3 command-line arguements. The first is the
1130 name of the event (see below). The second is the name of the
1131 md device which is affected, and the third is the name of a related
1132 device if relevant, such as a component device that has failed.
1136 is given, then a program or an E-mail address must be specified on the
1137 command line or in the config file. If neither are available, then
1139 will not monitor anything.
1143 will continue monitoring as long as something was found to monitor. If
1144 no program or email is given, then each event is reported to
1147 The different events are:
1151 .B DeviceDisappeared
1152 An md array which previously was configured appears to no longer be
1157 was told to monitor an array which is RAID0 or Linear, then it will
1159 .B DeviceDisappeared
1160 with the extra information
1162 This is because RAID0 and Linear do not support the device-failed,
1163 hot-spare and resync operations which are monitored.
1167 An md array started reconstruction.
1173 is 20, 40, 60, or 80, this indicates that rebuild has passed that many
1174 percentage of the total.
1178 An md array that was rebuilding, isn't any more, either because it
1179 finished normally or was aborted.
1183 An active component device of an array has been marked as faulty.
1187 A spare component device which was being rebuilt to replace a faulty
1192 A spare component device which was being rebuilt to replace a faulty
1193 device as been successfully rebuild and has been made active.
1197 A new md array has been detected in the
1203 A newly noticed array appears to be degraded. This message is not
1206 notices a drive failure which causes degradation, but only when
1208 notices that an array is degraded when it first sees the array.
1212 A spare drive has been moved from one array in a
1214 to another to allow a failed drive to be replaced.
1220 has been told, via the config file, that an array should have a certain
1221 number of spare devices, and
1223 detects that it has fewer that this number when it first sees the
1224 array, it will report a
1230 An array was found at startup, and the
1241 cause Email to be sent. All events cause the program to be run.
1242 The program is run with two or three arguments, they being the event
1243 name, the array device and possibly a second device.
1245 Each event has an associated array device (e.g.
1247 and possibly a second device. For
1252 the second device is the relevant component device.
1255 the second device is the array that the spare was moved from.
1259 to move spares from one array to another, the different arrays need to
1260 be labelled with the same
1262 in the configuration file. The
1264 name can be any string. It is only necessary that different spare
1265 groups use different names.
1269 detects that an array which is in a spare group has fewer active
1270 devices than necessary for the complete array, and has no spare
1271 devices, it will look for another array in the same spare group that
1272 has a full complement of working drive and a spare. It will then
1273 attempt to remove the spare from the second drive and add it to the
1275 If the removal succeeds but the adding fails, then it is added back to
1279 The GROW mode is used for changing the size or shape of an active
1281 For this to work, the kernel must support the necessary change.
1282 Various types of growth may be added during 2.6 development, possibly
1283 including restructuring a raid5 array to have more active devices.
1285 Currently the only support available is to
1287 change the "size" attribute
1288 for RAID1, RAID5 and RAID6.
1290 change the "raid-disks" attribute of RAID1.
1292 add a write-intent bitmap to a RAID1 array.
1295 Normally when an array is built the "size" it taken from the smallest
1296 of the drives. If all the small drives in an arrays are, one at a
1297 time, removed and replaced with larger drives, then you could have an
1298 array of large drives with only a small amount used. In this
1299 situation, changing the "size" with "GROW" mode will allow the extra
1300 space to start being used. If the size is increased in this way, a
1301 "resync" process will start to make sure the new parts of the array
1304 Note that when an array changes size, any filesystem that may be
1305 stored in the array will not automatically grow to use the space. The
1306 filesystem will need to be explicitly told to use the extra space.
1308 A RAID1 array can work with any number of devices from 1 upwards
1309 (though 1 is not very useful). There may be times which you want to
1310 increase or decrease the number of active devices. Note that this is
1311 different to hot-add or hot-remove which changes the number of
1314 When reducing the number of devices in a RAID1 array, the slots which
1315 are to be removed from the array must already be vacant. That is, the
1316 devices that which were in those slots must be failed and removed.
1318 When the number of devices is increased, any hot spares that are
1319 present may be activated immediately.
1321 A write-intent bitmap can be added to, or remove from, an active RAID1
1322 array. Either internal bitmap, of bitmaps stored in a separate file
1323 can be added. Note that if you add a bitmap stored in a file which is
1324 in a filesystem that is on the raid array being affected, the system
1325 will deadlock. The bitmap must be on a separate filesystem.
1329 .B " mdadm --query /dev/name-of-device"
1331 This will find out if a given device is a raid array, or is part of
1332 one, and will provide brief information about the device.
1334 .B " mdadm --assemble --scan"
1336 This will assemble and start all arrays listed in the standard confile
1337 file. This command will typically go in a system startup file.
1339 .B " mdadm --stop --scan"
1341 This will shut down all array that can be shut down (i.e. are not
1342 currently in use). This will typically go in a system shutdown script.
1344 .B " mdadm --follow --scan --delay=120"
1346 If (and only if) there is an Email address or program given in the
1347 standard config file, then
1348 monitor the status of all arrays listed in that file by
1349 polling them ever 2 minutes.
1351 .B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1"
1353 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
1356 .B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf"
1358 .B " mdadm --detail --scan >> mdadm.conf"
1360 This will create a prototype config file that describes currently
1361 active arrays that are known to be made from partitions of IDE or SCSI drives.
1362 This file should be reviewed before being used as it may
1363 contain unwanted detail.
1365 .B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf"
1367 .B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf"
1369 This will find what arrays could be assembled from existign IDE and
1370 SCSI whole drives (not partitions) and store the information is the
1371 format of a config file.
1372 This file is very likely to contain unwanted detail, particularly
1375 entries. It should be reviewed and edited before being used as an
1378 .B " mdadm --examine --brief --scan --config=partitions"
1380 .B " mdadm -Ebsc partitions"
1382 Create a list of devices by reading
1383 .BR /proc/partitions ,
1384 scan these for RAID superblocks, and printout a brief listing of all
1387 .B " mdadm -Ac partitions -m 0 /dev/md0"
1389 Scan all partitions and devices listed in
1390 .BR /proc/partitions
1393 out of all such devices with a RAID superblock with a minor number of 0.
1395 .B " mdadm --monitor --scan --daemonise > /var/run/mdadm"
1397 If config file contains a mail address or alert program, run mdadm in
1398 the background in monitor mode monitoring all md devices. Also write
1399 pid of mdadm daemon to
1400 .BR /var/run/mdadm .
1402 .B " mdadm --create --help"
1404 Providew help about the Create mode.
1406 .B " mdadm --config --help"
1408 Provide help about the format of the config file.
1412 Provide general help.
1423 lists all active md devices with information about them.
1425 uses this to find arrays when
1427 is given in Misc mode, and to monitor array reconstruction
1433 The config file lists which devices may be scanned to see if
1434 they contain MD super block, and gives identifying information
1435 (e.g. UUID) about known MD arrays. See
1441 While entries in the /dev directory can have any format you like,
1443 has an understanding of 'standard' formats which it uses to guide its
1444 behaviour when creating device files via the
1448 The standard names for non-partitioned arrays (the only sort of md
1449 array available in 2.4 and earlier) either of
1455 where NN is a number.
1456 The standard names for partitionable arrays (as available from 2.6
1463 Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
1467 was previously known as
1471 For information on the various levels of
1475 .UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1476 http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1479 for new releases of the RAID driver check out:
1482 .UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1483 ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1488 .UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
1489 http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
projects / thirdparty / mdadm.git / blob