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
38 is not a Software RAID mechanism, but does involve
41 each device is a path to one common physical storage device.
44 is also not true RAID, and it only involves one device. It
45 provides a layer over a true device that can be used to inject faults.
48 '''is a program that can be used to create, manage, and monitor
50 '''such it provides a similar set of functionality to the
53 '''The key differences between
60 '''is a single program and not a collection of programs.
63 '''can perform (almost) all of its functions without having a
64 '''configuration file and does not use one by default. Also
66 '''helps with management of the configuration
70 '''can provide information about your arrays (through Query, Detail, and Examine)
80 '''configuration file, at all. It has a different configuration file
81 '''with a different format and an different purpose.
84 mdadm has 7 major modes of operation:
87 Assemble the parts of a previously created
88 array into an active array. Components can be explicitly given
89 or can be searched for.
91 checks that the components
92 do form a bona fide array, and can, on request, fiddle superblock
93 information so as to assemble a faulty array.
97 Build an array that doesn't have per-device superblocks. For these
100 cannot differentiate between initial creation and subsequent assembly
101 of an array. It also cannot perform any checks that appropriate
102 devices have been requested. Because of this, the
104 mode should only be used together with a complete understanding of
109 Create a new array with per-device superblocks.
111 '''in several step create-add-add-run or it can all happen with one command.
115 This is for doing things to specific components of an array such as
116 adding new spares and removing faulty devices.
120 This mode allows operations on independent devices such as examine MD
121 superblocks, erasing old superblocks and stopping active arrays.
124 .B "Follow or Monitor"
125 Monitor one or more md devices and act on any state changes. This is
126 only meaningful for raid1, 4, 5, 6 or multipath arrays as
127 only these have interesting state. raid0 or linear never have
128 missing, spare, or failed drives, so there is nothing to monitor.
132 Grow (or shrink) an array, or otherwise reshape it in some way.
133 Currently supported growth options including changing the active size
134 of componenet devices in RAID level 1/4/5/6 and changing the number of
135 active devices in RAID1.
139 Available options are:
142 .BR -A ", " --assemble
143 Assemble a pre-existing array.
147 Build a legacy array without superblocks.
155 Examine a device to see
156 (1) if it is an md device and (2) if it is a component of an md
158 Information about what is discovered is presented.
162 Print detail of one or more md devices.
165 .BR -E ", " --examine
166 Print content of md superblock on device(s).
169 .BR -F ", " --follow ", " --monitor
176 Change the size or shape of an active array.
179 .BR -X ", " --examine-bitmap
180 Report information about a bitmap file.
184 Display general help message or, after one of the above options, a
185 mode specific help message.
189 Display more detailed help about command line parsing and some commonly
193 .BR -V ", " --version
194 Print version information for mdadm.
197 .BR -v ", " --verbose
198 Be more verbose about what is happening. This can be used twice to be
200 The extra verbosity currently only affects
203 .BR "--examine --scan" .
207 Avoid printing purely informative messages. With this,
209 will be silent unless there is something really important to report.
213 Be less verbose. This is used with
221 gives an intermediate level of verbosity.
224 .BR -W ", " --write-mostly
225 subsequent devices lists in a
230 command will be flagged as 'write-mostly'. This is valid for RAID1
231 only and means that the 'md' driver will avoid reading from these
232 devices if at all possible. This can be useful if mirroring over a
236 .BR -b ", " --bitmap=
237 Give the name of a bitmap file to use with this array. Can be used
238 with --create (file should not exist), --assemble (file should
239 exist), of --grow (file should not exist).
243 can be used to indicate that the bitmap should be stored in the array,
244 near the superblock. There is a limited amount of space for such
245 bitmaps, but it is often sufficient.
249 can be given when used with --grow to remove a bitmap.
253 Set the Chunksize of the bitmap. Each bit corresponds to that many
254 Kilobytes of storage. Default is 4.
258 Specify that write-behind mode should be enabled (valid for RAID1
259 only). If an argument is specified, it will set the maximum number
260 of outstanding writes allowed. The default value is 256.
261 A write-intent bitmap is required in order to use write-behind
262 mode, and write-behind is only attempted on drives marked as
268 Be more forceful about certain operations. See the various modes of
269 the exact meaning of this option in different contexts.
272 .BR -c ", " --config=
273 Specify the config file. Default is
274 .BR /etc/mdadm.conf .
275 If the config file given is
277 then nothing will be read, but
279 will act as though the config file contained exactly
280 .B "DEVICE partitions"
283 to find a list of devices to scan.
286 is given for the config file, then
288 will act as though the config file were empty.
294 for missing information.
295 In general, this option gives
297 permission to get any missing information, like component devices,
298 array devices, array identities, and alert destination from the
300 .BR /etc/mdadm.conf .
301 One exception is MISC mode when using
307 says to get a list of array devices from
311 .B -e ", " --metadata=
312 Declare the style of superblock (raid metadata) to be used. The
313 default is 0.90 for --create, and to guess for other operations.
317 .IP "0, 0.90, default"
318 Use the original 0.90 format superblock. This format limits arrays to
319 28 componenet devices and limits component devices of levels 1 and
320 greater to 2 terabytes.
321 .IP "1, 1.0, 1.1, 1.2"
322 Use the new version-1 format superblock. This has few restrictions.
323 The different subversion store the superblock at different locations
324 on the device, either at the end (for 1.0), at the start (for 1.1) or
325 4K from the start (for 1.2).
328 .SH For create or build:
332 Specify chunk size of kibibytes. The default is 64.
336 Specify rounding factor for linear array (==chunk size)
340 Set raid level. When used with
342 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
343 raid5, 5, raid6, 6, multipath, mp, fautly. Obviously some of these are synonymous.
347 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
350 .BR -p ", " --parity=
351 Set raid5 parity algorithm. Options are:
356 la, ra, ls, rs. The default is left-symmetric.
358 This option is also used to set the failure mode for
376 Each mode can be followed by a number which is used as a period
377 between fault generation. Without a number, the fault is generated
378 once on the first relevant request. With a number, the fault will be
379 generated after that many request, and will continue to be generated
380 every time the period elapses.
382 Multiple failure modes can be current simultaneously by using the
383 "--grow" option to set subsequent failure modes.
385 "clear" or "none" will remove any pending or periodic failure modes,
386 and "flush" will clear any persistant faults.
388 To set the parity with "--grow", the level of the array ("faulty")
389 must be specified before the fault mode is specified.
396 .BR -b ", " --bitmap=
397 Specify a file to store a write-intent bitmap in. The file should not
398 exist unless --force is also given. The same file should be provided
399 when assembling the array.
403 Specifty the chunksize for the bitmap.
406 .BR -n ", " --raid-devices=
407 Specify the number of active devices in the array. This, plus the
408 number of spare devices (see below) must equal the number of
410 (including "\fBmissing\fP" devices)
411 that are listed on the command line for
413 Setting a value of 1 is probably
414 a mistake and so requires that
416 be specified first. A value of 1 will then be allowed for linear,
417 multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
419 This number can only be changed using
421 for RAID1 arrays, and only on kernels which provide necessary support.
424 .BR -x ", " --spare-devices=
425 Specify the number of spare (eXtra) devices in the initial array.
426 Spares can also be added
427 and removed later. The number of component devices listed
428 on the command line must equal the number of raid devices plus the
429 number of spare devices.
434 Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6.
435 This must be a multiple of the chunk size, and must leave about 128Kb
436 of space at the end of the drive for the RAID superblock.
437 If this is not specified
438 (as it normally is not) the smallest drive (or partition) sets the
439 size, though if there is a variance among the drives of greater than 1%, a warning is
442 This value can be set with
444 for RAID level 1/4/5/6. If the array was created with a size smaller
445 than the currently active drives, the extra space can be accessed
448 The size can be given as
450 which means to choose the largest size that fits on all current drives.
456 that the array pre-existed and is known to be clean. This is only
457 really useful for Building RAID1 array. Only use this if you really
458 know what you are doing. This is currently only supported for --build.
464 for the array. This is currently only effective when creating an
465 array with a version-1 superblock. The name is a simple textual
466 string that can be used to identify array components when assembling.
472 run the array, even if some of the components
473 appear to be active in another array or filesystem. Normally
475 will ask for confirmation before including such components in an
476 array. This option causes that question to be suppressed.
482 accept the geometry and layout specified without question. Normally
484 will not allow creation of an array with only one device, and will try
485 to create a raid5 array with one missing drive (as this makes the
486 initial resync work faster). With
489 will not try to be so clever.
492 .BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}"
493 Instruct mdadm to create the device file if needed, possibly allocating
494 an unused minor number. "md" causes a non-partitionable array
495 to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
496 later) to be used. "yes" requires the named md device to have a
497 'standard' format, and the type and minor number will be determined
498 from this. See DEVICE NAMES below.
500 The argument can also come immediately after
505 is also given, then any
507 entries in the config file will over-ride the
509 instruction given on the command line.
511 For partitionable arrays,
513 will create the device file for the whole array and for the first 4
514 partitions. A different number of partitions can be specified at the
515 end of this option (e.g.
517 If the device name ends with a digit, the partition names add a'p',
518 and a number, e.g. "/dev/home1p3". If there is no
519 trailing digit, then the partition names just have a number added,
520 e.g. "/dev/scratch3".
522 If the md device name is in a 'standard' format as described in DEVICE
523 NAMES, then it will be created, if necessary, with the appropriate
524 number based on that name. If the device name is not in one of these
525 formats, then a unused minor number will be allocated. The minor
526 number will be considered unused if there is no active array for that
527 number, and there is no entry in /dev for that number and with a
534 uuid of array to assemble. Devices which don't have this uuid are
538 .BR -m ", " --super-minor=
539 Minor number of device that array was created for. Devices which
540 don't have this minor number are excluded. If you create an array as
541 /dev/md1, then all superblocks will contain the minor number 1, even if
542 the array is later assembled as /dev/md2.
544 Giving the literal word "dev" for
548 to use the minor number of the md device that is being assembled.
552 will look for super blocks with a minor number of 0.
556 Specify the name of the array to assemble. This must be the name
557 that was specified when creating the array.
561 Assemble the array even if some superblocks appear out-of-date
565 Attempt to start the array even if fewer drives were given than are
566 needed for a full array. Normally if not all drives are found and
568 is not used, then the array will be assembled but not started.
571 an attempt will be made to start it anyway.
574 .BR -a ", " "--auto{=no,yes,md,mdp,part}"
575 See this option under Create and Build options.
578 .BR -b ", " --bitmap=
579 Specify the bitmap file that was given when the array was created.
582 .BR -U ", " --update=
583 Update the superblock on each device while assembling the array. The
584 argument given to this flag can be one of
594 option will adjust the superblock of an array what was created on a Sparc
595 machine running a patched 2.2 Linux kernel. This kernel got the
596 alignment of part of the superblock wrong. You can use the
597 .B "--examine --sparc2.2"
600 to see what effect this would have.
604 option will update the
606 field on each superblock to match the minor number of the array being
607 assembled. This is not needed on 2.6 and later kernels as they make
608 this adjustment automatically.
612 option will cause the array to be marked
614 meaning that any redundancy in the array (e.g. parity for raid5,
615 copies for raid1) may be incorrect. This will cause the raid system
616 to perform a "resync" pass to make sure that all redundant information
621 option allows arrays to be moved between machines with different
623 When assembling such an array for the first time after a move, giving
624 .B "--update=byteorder"
627 to expect superblocks to have their byteorder reversed, and will
628 correct that order before assembling the array. This is only valid
629 with original (Verion 0.90) superblocks.
633 option will correct the summaries in the superblock. That is the
634 counts of total, working, active, failed, and spare devices.
641 hotadd listed devices.
645 Listed devices are assumed to have recently been part of the array,
646 and they are re-added. This is only different from --add when a
647 write-intent bitmap is present. It causes only those parts of the
648 device that have changed since the device was removed from the array
651 This flag is only needed with arrays that are built without a
652 superblock (i.e. --build, not --create). For array with a superblock,
654 checks if a superblock is present and automatically determines if a
655 re-add is appropriate.
659 remove listed devices. They must not be active. i.e. they should
660 be failed or spare devices.
664 mark listed devices as faulty.
670 .SH For Examine mode:
674 If an array was created on a 2.2 Linux kernel patched with RAID
675 support, the superblock will have been created incorrectly, or at
676 least incompatibly with 2.4 and later kernels. Using the
680 will fix the superblock before displaying it. If this appears to do
681 the right thing, then the array can be successfully assembled using
682 .BR "--assemble --update=sparc2.2" .
688 start a partially built array.
692 deactivate array, releasing all resources.
695 .BR -o ", " --readonly
696 mark array as readonly.
699 .BR -w ", " --readwrite
700 mark array as readwrite.
704 If the device contains a valid md superblock, the block is
705 over-written with zeros. With
707 the block where the superblock would be is over-written even if it
708 doesn't appear to be valid.
716 is set to reflect the status of the device.
718 .SH For Monitor mode:
721 Give a mail address to send alerts to.
724 .BR -p ", " --program ", " --alert
725 Give a program to be run whenever an event is detected.
729 Give a delay in seconds.
731 polls the md arrays and then waits this many seconds before polling
732 again. The default is 60 seconds.
735 .BR -f ", " --daemonise
738 to run as a background daemon if it decides to monitor anything. This
739 causes it to fork and run in the child, and to disconnect form the
740 terminal. The process id of the child is written to stdout.
743 which will only continue monitoring if a mail address or alert program
744 is found in the config file.
747 .BR -i ", " --pid-file
750 is running in daemon mode, write the pid of the daemon process to
751 the specified file, instead of printing it on standard output.
754 .BR -1 ", " --oneshot
755 Check arrays only once. This will generate
757 events and more significantly
763 .B " mdadm --monitor --scan -1"
765 from a cron script will ensure regular notification of any degraded arrays.
771 alert for every array found at startup. This alert gets mailed and
772 passed to the alert program. This can be used for testing that alert
773 message do get through successfully.
780 .I md-device options-and-component-devices...
783 .B mdadm --assemble --scan
784 .I md-devices-and-options...
787 .B mdadm --assemble --scan
791 This usage assembles one or more raid arrays from pre-existing components.
792 For each array, mdadm needs to know the md device, the identity of the
793 array, and a number of component-devices. These can be found in a number of ways.
795 In the first usage example (without the
797 the first device given is the md device.
798 In the second usage example, all devices listed are treated as md
799 devices and assembly is attempted.
800 In the third (where no devices are listed) all md devices that are
801 listed in the configuration file are assembled.
803 If precisely one device is listed, but
809 was given and identify information is extracted from the configuration file.
811 The identity can be given with the
815 option, can be found in the config file, or will be taken from the
816 super block on the first component-device listed on the command line.
818 Devices can be given on the
820 command line or in the config file. Only devices which have an md
821 superblock which contains the right identity will be considered for
824 The config file is only used if explicitly named with
826 or requested with (a possibly implicit)
834 is not given, then the config file will only be used to find the
835 identity of md arrays.
837 Normally the array will be started after it is assembled. However if
839 is not given and insufficient drives were listed to start a complete
840 (non-degraded) array, then the array is not started (to guard against
841 usage errors). To insist that the array be started in this case (as
842 may work for RAID1, 4, 5 or 6), give the
848 option is given, either on the command line (--auto) or in the
849 configuration file (e.g. auto=part), then
851 will create the md device if necessary or will re-create it if it
852 doesn't look usable as it is.
854 This can be useful for handling partitioned devices (which don't have
855 a stable device number - it can change after a reboot) and when using
856 "udev" to manage your
858 tree (udev cannot handle md devices because of the unusual device
859 initialisation conventions).
861 If the option to "auto" is "mdp" or "part" or (on the command line
862 only) "p", then mdadm will create a partitionable array, using the
863 first free one that is not inuse, and does not already have an entry
864 in /dev (apart from numeric /dev/md* entries).
866 If the option to "auto" is "yes" or "md" or (on the command line)
867 nothing, then mdadm will create a traditional, non-partitionable md
870 It is expected that the "auto" functionality will be used to create
871 device entries with meaningful names such as "/dev/md/home" or
872 "/dev/md/root", rather than names based on the numerical array number.
874 When using this option to create a partitionable array, the device
875 files for the first 4 partitions are also created. If a different
876 number is required it can be simply appended to the auto option.
877 e.g. "auto=part8". Partition names are created by appending a digit
878 string to the device name, with an intervening "p" if the device name
883 option is also available in Build and Create modes. As those modes do
884 not use a config file, the "auto=" config option does not apply to
895 .BI --raid-devices= Z
899 This usage is similar to
901 The difference is that it creates an array without a superblock. With
902 these arrays there is no difference between initially creating the array and
903 subsequently assembling the array, except that hopefully there is useful
904 data there in the second case.
906 The level may raid0, linear, multipath, or faulty, or one of their
907 synonyms. All devices must be listed and the array will be started
919 .BI --raid-devices= Z
923 This usage will initialise a new md array, associate some devices with
924 it, and activate the array.
928 option is given (as described in more detail in the section on
929 Assemble mode), then the md device will be created with a suitable
930 device number if necessary.
932 As devices are added, they are checked to see if they contain raid
933 superblocks or filesystems. They are also checked to see if the variance in
934 device size exceeds 1%.
936 If any discrepancy is found, the array will not automatically be run, though
939 can override this caution.
941 To create a "degraded" array in which some devices are missing, simply
942 give the word "\fBmissing\fP"
943 in place of a device name. This will cause
945 to leave the corresponding slot in the array empty.
946 For a RAID4 or RAID5 array at most one slot can be
947 "\fBmissing\fP"; for a RAID6 array at most two slots.
948 For a RAID1 array, only one real device needs to be given. All of the
952 When creating a RAID5 array,
954 will automatically create a degraded array with an extra spare drive.
955 This is because building the spare into a degraded array is in general faster than resyncing
956 the parity on a non-degraded, but not clean, array. This feature can
957 be over-ridden with the
963 '''option is given, it is not necessary to list any component-devices in this command.
964 '''They can be added later, before a
968 '''is given, the apparent size of the smallest drive given is used.
970 The General Management options that are valid with --create are:
973 insist on running the array even if some devices look like they might
978 start the array readonly - not supported yet.
985 .I options... devices...
988 This usage will allow individual devices in an array to be failed,
989 removed or added. It is possible to perform multiple operations with
990 on command. For example:
992 .B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1"
998 and will then remove it from the array and finally add it back
999 in as a spare. However only one md array can be affected by a single
1010 MISC mode includes a number of distinct operations that
1011 operate on distinct devices. The operations are:
1014 The device is examined to see if it is
1015 (1) an active md array, or
1016 (2) a component of an md array.
1017 The information discovered is reported.
1021 The device should be an active md device.
1023 will display a detailed description of the array.
1027 will cause the output to be less detailed and the format to be
1028 suitable for inclusion in
1029 .BR /etc/mdadm.conf .
1032 will normally be 0 unless
1034 failed to get useful information about the device(s). However if the
1036 option is given, then the exit status will be:
1040 The array is functioning normally.
1043 The array has at least one failed device.
1046 The array has multiple failed devices and hence is unusable (raid4 or
1050 There was an error while trying to get information about the device.
1055 The device should be a component of an md array.
1057 will read the md superblock of the device and display the contents.
1062 then multiple devices that are components of the one array
1063 are grouped together and reported in a single entry suitable
1065 .BR /etc/mdadm.conf .
1069 without listing any devices will cause all devices listed in the
1070 config file to be examined.
1074 The devices should be active md arrays which will be deactivated, as
1075 long as they are not currently in use.
1079 This will fully activate a partially assembled md array.
1083 This will mark an active array as read-only, providing that it is
1084 not currently being used.
1090 array back to being read/write.
1094 For all operations except
1097 will cause the operation to be applied to all arrays listed in
1102 causes all devices listed in the config file to be examined.
1110 .I options... devices...
1115 to periodically poll a number of md arrays and to report on any events
1118 will never exit once it decides that there are arrays to be checked,
1119 so it should normally be run in the background.
1121 As well as reporting events,
1123 may move a spare drive from one array to another if they are in the
1126 and if the destination array has a failed drive but no spares.
1128 If any devices are listed on the command line,
1130 will only monitor those devices. Otherwise all arrays listed in the
1131 configuration file will be monitored. Further, if
1133 is given, then any other md devices that appear in
1135 will also be monitored.
1137 The result of monitoring the arrays is the generation of events.
1138 These events are passed to a separate program (if specified) and may
1139 be mailed to a given E-mail address.
1141 When passing event to program, the program is run once for each event
1142 and is given 2 or 3 command-line arguements. The first is the
1143 name of the event (see below). The second is the name of the
1144 md device which is affected, and the third is the name of a related
1145 device if relevant, such as a component device that has failed.
1149 is given, then a program or an E-mail address must be specified on the
1150 command line or in the config file. If neither are available, then
1152 will not monitor anything.
1156 will continue monitoring as long as something was found to monitor. If
1157 no program or email is given, then each event is reported to
1160 The different events are:
1164 .B DeviceDisappeared
1165 An md array which previously was configured appears to no longer be
1170 was told to monitor an array which is RAID0 or Linear, then it will
1172 .B DeviceDisappeared
1173 with the extra information
1175 This is because RAID0 and Linear do not support the device-failed,
1176 hot-spare and resync operations which are monitored.
1180 An md array started reconstruction.
1186 is 20, 40, 60, or 80, this indicates that rebuild has passed that many
1187 percentage of the total.
1191 An md array that was rebuilding, isn't any more, either because it
1192 finished normally or was aborted.
1196 An active component device of an array has been marked as faulty.
1200 A spare component device which was being rebuilt to replace a faulty
1205 A spare component device which was being rebuilt to replace a faulty
1206 device as been successfully rebuild and has been made active.
1210 A new md array has been detected in the
1216 A newly noticed array appears to be degraded. This message is not
1219 notices a drive failure which causes degradation, but only when
1221 notices that an array is degraded when it first sees the array.
1225 A spare drive has been moved from one array in a
1227 to another to allow a failed drive to be replaced.
1233 has been told, via the config file, that an array should have a certain
1234 number of spare devices, and
1236 detects that it has fewer that this number when it first sees the
1237 array, it will report a
1243 An array was found at startup, and the
1254 cause Email to be sent. All events cause the program to be run.
1255 The program is run with two or three arguments, they being the event
1256 name, the array device and possibly a second device.
1258 Each event has an associated array device (e.g.
1260 and possibly a second device. For
1265 the second device is the relevant component device.
1268 the second device is the array that the spare was moved from.
1272 to move spares from one array to another, the different arrays need to
1273 be labelled with the same
1275 in the configuration file. The
1277 name can be any string. It is only necessary that different spare
1278 groups use different names.
1282 detects that an array which is in a spare group has fewer active
1283 devices than necessary for the complete array, and has no spare
1284 devices, it will look for another array in the same spare group that
1285 has a full complement of working drive and a spare. It will then
1286 attempt to remove the spare from the second drive and add it to the
1288 If the removal succeeds but the adding fails, then it is added back to
1292 The GROW mode is used for changing the size or shape of an active
1294 For this to work, the kernel must support the necessary change.
1295 Various types of growth may be added during 2.6 development, possibly
1296 including restructuring a raid5 array to have more active devices.
1298 Currently the only support available is to
1300 change the "size" attribute
1301 for RAID1, RAID5 and RAID6.
1303 change the "raid-disks" attribute of RAID1.
1305 add a write-intent bitmap to a RAID1 array.
1308 Normally when an array is built the "size" it taken from the smallest
1309 of the drives. If all the small drives in an arrays are, one at a
1310 time, removed and replaced with larger drives, then you could have an
1311 array of large drives with only a small amount used. In this
1312 situation, changing the "size" with "GROW" mode will allow the extra
1313 space to start being used. If the size is increased in this way, a
1314 "resync" process will start to make sure the new parts of the array
1317 Note that when an array changes size, any filesystem that may be
1318 stored in the array will not automatically grow to use the space. The
1319 filesystem will need to be explicitly told to use the extra space.
1321 A RAID1 array can work with any number of devices from 1 upwards
1322 (though 1 is not very useful). There may be times which you want to
1323 increase or decrease the number of active devices. Note that this is
1324 different to hot-add or hot-remove which changes the number of
1327 When reducing the number of devices in a RAID1 array, the slots which
1328 are to be removed from the array must already be vacant. That is, the
1329 devices that which were in those slots must be failed and removed.
1331 When the number of devices is increased, any hot spares that are
1332 present will be activated immediately.
1334 A write-intent bitmap can be added to, or remove from, an active RAID1
1335 array. Either internal bitmap, of bitmaps stored in a separate file
1336 can be added. Note that if you add a bitmap stored in a file which is
1337 in a filesystem that is on the raid array being affected, the system
1338 will deadlock. The bitmap must be on a separate filesystem.
1342 .B " mdadm --query /dev/name-of-device"
1344 This will find out if a given device is a raid array, or is part of
1345 one, and will provide brief information about the device.
1347 .B " mdadm --assemble --scan"
1349 This will assemble and start all arrays listed in the standard confile
1350 file. This command will typically go in a system startup file.
1352 .B " mdadm --stop --scan"
1354 This will shut down all array that can be shut down (i.e. are not
1355 currently in use). This will typically go in a system shutdown script.
1357 .B " mdadm --follow --scan --delay=120"
1359 If (and only if) there is an Email address or program given in the
1360 standard config file, then
1361 monitor the status of all arrays listed in that file by
1362 polling them ever 2 minutes.
1364 .B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1"
1366 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
1369 .B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf"
1371 .B " mdadm --detail --scan >> mdadm.conf"
1373 This will create a prototype config file that describes currently
1374 active arrays that are known to be made from partitions of IDE or SCSI drives.
1375 This file should be reviewed before being used as it may
1376 contain unwanted detail.
1378 .B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf"
1380 .B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf"
1382 This will find what arrays could be assembled from existign IDE and
1383 SCSI whole drives (not partitions) and store the information is the
1384 format of a config file.
1385 This file is very likely to contain unwanted detail, particularly
1388 entries. It should be reviewed and edited before being used as an
1391 .B " mdadm --examine --brief --scan --config=partitions"
1393 .B " mdadm -Ebsc partitions"
1395 Create a list of devices by reading
1396 .BR /proc/partitions ,
1397 scan these for RAID superblocks, and printout a brief listing of all
1400 .B " mdadm -Ac partitions -m 0 /dev/md0"
1402 Scan all partitions and devices listed in
1403 .BR /proc/partitions
1406 out of all such devices with a RAID superblock with a minor number of 0.
1408 .B " mdadm --monitor --scan --daemonise > /var/run/mdadm"
1410 If config file contains a mail address or alert program, run mdadm in
1411 the background in monitor mode monitoring all md devices. Also write
1412 pid of mdadm daemon to
1413 .BR /var/run/mdadm .
1415 .B " mdadm --create --help"
1417 Providew help about the Create mode.
1419 .B " mdadm --config --help"
1421 Provide help about the format of the config file.
1425 Provide general help.
1436 lists all active md devices with information about them.
1438 uses this to find arrays when
1440 is given in Misc mode, and to monitor array reconstruction
1446 The config file lists which devices may be scanned to see if
1447 they contain MD super block, and gives identifying information
1448 (e.g. UUID) about known MD arrays. See
1454 While entries in the /dev directory can have any format you like,
1456 has an understanding of 'standard' formats which it uses to guide its
1457 behaviour when creating device files via the
1461 The standard names for non-partitioned arrays (the only sort of md
1462 array available in 2.4 and earlier) either of
1468 where NN is a number.
1469 The standard names for partitionable arrays (as available from 2.6
1476 Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
1480 was previously known as
1484 is completely separate from the
1486 package, and does not use the
1488 configuration file at all.
1491 For information on the various levels of
1495 .UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1496 http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1499 '''for new releases of the RAID driver check out:
1502 '''.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1503 '''ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1508 '''.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
1509 '''http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
1512 The lastest version of
1514 should always be available from
1516 .UR http://www.kernel.org/pub/linux/utils/raid/mdadm/
1517 http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob