.\" -*- nroff -*-
-.TH MDADM 8 "" v1.8.0
+.TH MDADM 8 "" v2.2
.SH NAME
mdadm \- manage MD devices
.I aka
.BR RAID4 ,
.BR RAID5 ,
.BR RAID6 ,
+.BR RAID10 ,
.BR MULTIPATH ,
and
.BR FAULTY .
-.B MULTIPATH is not a Software RAID mechanism, but does involve
+.B MULTIPATH
+is not a Software RAID mechanism, but does involve
multiple devices. For
.B MULTIPATH
each device is a path to one common physical storage device.
-.B FAULTY is also no true RAID, and it only involves one device. It
+.B FAULTY
+is also not true RAID, and it only involves one device. It
provides a layer over a true device that can be used to inject faults.
-.B mdadm
-is a program that can be used to create, manage, and monitor
-MD devices. As
-such it provides a similar set of functionality to the
-.B raidtools
-packages.
-The key differences between
-.B mdadm
-and
-.B raidtools
-are:
-.IP \(bu 4
-.B mdadm
-is a single program and not a collection of programs.
-.IP \(bu 4
-.B mdadm
-can perform (almost) all of its functions without having a
-configuration file and does not use one by default. Also
-.B mdadm
-helps with management of the configuration
-file.
-.IP \(bu 4
-.B mdadm
-can provide information about your arrays (through Query, Detail, and Examine)
-that
-.B raidtools
-cannot.
-.P
-.I mdadm
-does not use
-.IR /etc/raidtab ,
-the
-.B raidtools
-configuration file, at all. It has a different configuration file
-with a different format and an different purpose.
+'''.B mdadm
+'''is a program that can be used to create, manage, and monitor
+'''MD devices. As
+'''such it provides a similar set of functionality to the
+'''.B raidtools
+'''packages.
+'''The key differences between
+'''.B mdadm
+'''and
+'''.B raidtools
+'''are:
+'''.IP \(bu 4
+'''.B mdadm
+'''is a single program and not a collection of programs.
+'''.IP \(bu 4
+'''.B mdadm
+'''can perform (almost) all of its functions without having a
+'''configuration file and does not use one by default. Also
+'''.B mdadm
+'''helps with management of the configuration
+'''file.
+'''.IP \(bu 4
+'''.B mdadm
+'''can provide information about your arrays (through Query, Detail, and Examine)
+'''that
+'''.B raidtools
+'''cannot.
+'''.P
+'''.I mdadm
+'''does not use
+'''.IR /etc/raidtab ,
+'''the
+'''.B raidtools
+'''configuration file, at all. It has a different configuration file
+'''with a different format and an different purpose.
.SH MODES
mdadm has 7 major modes of operation:
.TP
.B Build
-Build a legacy array without per-device superblocks.
+Build an array that doesn't have per-device superblocks. For these
+sorts of arrays,
+.I mdadm
+cannot differentiate between initial creation and subsequent assembly
+of an array. It also cannot perform any checks that appropriate
+devices have been requested. Because of this, the
+.B Build
+mode should only be used together with a complete understanding of
+what you are doing.
.TP
.B Create
.TP
.B "Follow or Monitor"
Monitor one or more md devices and act on any state changes. This is
-only meaningful for raid1, 4, 5, 6 or multipath arrays as
+only meaningful for raid1, 4, 5, 6, 10 or multipath arrays as
only these have interesting state. raid0 or linear never have
missing, spare, or failed drives, so there is nothing to monitor.
.BR -G ", " --grow
Change the size or shape of an active array.
+.TP
+.BR -X ", " --examine-bitmap
+Report information about a bitmap file.
+
.TP
.BR -h ", " --help
-Display help message or, after above option, mode specific help
-message.
+Display general help message or, after one of the above options, a
+mode specific help message.
.TP
.B --help-options
.TP
.BR -v ", " --verbose
-Be more verbose about what is happening.
+Be more verbose about what is happening. This can be used twice to be
+extra-verbose.
+The extra verbosity currently only affects
+.B --detail --scan
+and
+.BR "--examine --scan" .
+
+.TP
+.BR -q ", " --quiet
+Avoid printing purely informative messages. With this,
+.B mdadm
+will be silent unless there is something really important to report.
.TP
.BR -b ", " --brief
.B --detail
and
.BR --examine .
+Using
+.B --brief
+with
+.B --verbose
+gives an intermediate level of verbosity.
+
+.TP
+.BR -W ", " --write-mostly
+subsequent devices lists in a
+.BR --build ,
+.BR --create ,
+or
+.B --add
+command will be flagged as 'write-mostly'. This is valid for RAID1
+only and means that the 'md' driver will avoid reading from these
+devices if at all possible. This can be useful if mirroring over a
+slow link.
+
+.TP
+.BR -b ", " --bitmap=
+Give the name of a bitmap file to use with this array. Can be used
+with --create (file should not exist), --assemble (file should
+exist), of --grow (file should not exist).
+
+The file
+.B internal
+can be used to indicate that the bitmap should be stored in the array,
+near the superblock. There is a limited amount of space for such
+bitmaps, but it is often sufficient.
+
+The file
+.B none
+can be given when used with --grow to remove a bitmap.
+
+.TP
+.BR --bitmap-chunk=
+Set the Chunksize of the bitmap. Each bit corresponds to that many
+Kilobytes of storage. Default is 4.
+
+.TP
+.BR --write-behind=
+Specify that write-behind mode should be enabled (valid for RAID1
+only). If an argument is specified, it will set the maximum number
+of outstanding writes allowed. The default value is 256.
+A write-intent bitmap is required in order to use write-behind
+mode, and write-behind is only attempted on drives marked as
+.IR write-mostly .
+
.TP
.BR -f ", " --force
says to get a list of array devices from
.BR /proc/mdstat .
+.TP
+.B -e ", " --metadata=
+Declare the style of superblock (raid metadata) to be used. The
+default is 0.90 for --create, and to guess for other operations.
+
+Options are:
+.RS
+.IP "0, 0.90, default"
+Use the original 0.90 format superblock. This format limits arrays to
+28 componenet devices and limits component devices of levels 1 and
+greater to 2 terabytes.
+.IP "1, 1.0, 1.1, 1.2"
+Use the new version-1 format superblock. This has few restrictions.
+The different subversion store the superblock at different locations
+on the device, either at the end (for 1.0), at the start (for 1.1) or
+4K from the start (for 1.2).
+.RE
+
.SH For create or build:
.TP
Set raid level. When used with
.IR --create ,
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
-raid5, 5, raid6, 6, multipath, mp, fautly. Obviously some of these are synonymous.
+raid5, 5, raid6, 6, raid10, 10, multipath, mp, fautly. Obviously some of these are synonymous.
When used with
.IR --build ,
-only linear, raid0, 0, stripe are valid.
+only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
.TP
-.BR -p ", " --parity=
-Set raid5 parity algorithm. Options are:
+.BR -p ", " --layout=
+This option configures the fine details of data layout for raid5,
+and raid10 arrays, and controls the failure modes for
+.IR faulty .
+
+The layout of the raid5 parity block can be one of
left-asymmetric,
left-symmetric,
right-asymmetric,
right-symmetric,
la, ra, ls, rs. The default is left-symmetric.
-This option is also used to set the failure mode for
-.IR faulty .
-The options are:
+When setting the failure mode for
+.I faulty
+the options are:
write-transient,
wt,
read-transient,
To set the parity with "--grow", the level of the array ("faulty")
must be specified before the fault mode is specified.
+Finally, the layout options for RAID10 are either 'n' or 'p' followed
+by a small number. The default is 'n2'.
+
+.I n
+signals 'near' copies (multiple copies of one data block are at
+similar offsets in different devices) while
+.I f
+signals 'far' copies
+(multiple copies have very different offsets). See md(4) for more
+detail about 'near' and 'far'.
+
+The number is the number of copies of each datablock. 2 is normal, 3
+can be useful. This number can be at most equal to the number of
+devices in the array. It does not need to divide evenly into that
+number (e.g. it is perfectly legal to have an 'n2' layout for an array
+with an odd number of devices).
+
+.TP
+.BR --parity=
+same as --layout (thus explaining the p of
+.IR -p ).
+
.TP
-.BR --layout=
-same as --parity
+.BR -b ", " --bitmap=
+Specify a file to store a write-intent bitmap in. The file should not
+exist unless --force is also given. The same file should be provided
+when assembling the array.
+
+.TP
+.BR --bitmap-chunk=
+Specifty the chunksize for the bitmap.
.TP
.BR -n ", " --raid-devices=
than the currently active drives, the extra space can be accessed
using
.BR --grow .
+The size can be given as
+.B max
+which means to choose the largest size that fits on all current drives.
.TP
.BR --assume-clean
Tell
.I mdadm
-that the array pre-existed and is known to be clean. This is only
-really useful for Building RAID1 array. Only use this if you really
-know what you are doing. This is currently only supported for --build.
+that the array pre-existed and is known to be clean. It can be useful
+when trying to recover from a major failure as you can be sure that no
+data will be affected unless you actually write to the array. It can
+also be used when creating a RAID1 or RAID10 if you want to avoid the
+initial resync, however this practice - while normally safe - is not
+recommended. Use this ony if you really know what you are doing.
+
+.TP
+.BR -N ", " --name=
+Set a
+.B name
+for the array. This is currently only effective when creating an
+array with a version-1 superblock. The name is a simple textual
+string that can be used to identify array components when assembling.
.TP
.BR -R ", " --run
.TP
.BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}"
-Instruct mdadm to create the device file if needed, and to allocate
-an unused minor number. "yes" or "md" causes a non-partitionable array
+Instruct mdadm to create the device file if needed, possibly allocating
+an unused minor number. "md" causes a non-partitionable array
to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
-later) to be used. The argumentment can also come immediately after
+later) to be used. "yes" requires the named md device to haveo
+a 'standard' format, and the type and minor number will be determined
+from this. See DEVICE NAMES below.
+
+The argument can also come immediately after
"-a". e.g. "-ap".
+If
+.I --scan
+is also given, then any
+.I auto=
+entries in the config file will over-ride the
+.I --auto
+instruction given on the command line.
+
For partitionable arrays,
.I mdadm
will create the device file for the whole array and for the first 4
partitions. A different number of partitions can be specified at the
end of this option (e.g.
.BR --auto=p7 ).
-If the device name ends with a digit, the partition names add an
-underscore, a 'p', and a number, e.g. "/dev/home1_p3". If there is no
+If the device name ends with a digit, the partition names add a'p',
+and a number, e.g. "/dev/home1p3". If there is no
trailing digit, then the partition names just have a number added,
e.g. "/dev/scratch3".
+If the md device name is in a 'standard' format as described in DEVICE
+NAMES, then it will be created, if necessary, with the appropriate
+number based on that name. If the device name is not in one of these
+formats, then a unused minor number will be allocated. The minor
+number will be considered unused if there is no active array for that
+number, and there is no entry in /dev for that number and with a
+non-standard name.
+
.SH For assemble:
.TP
.M --super-minor=dev
will look for super blocks with a minor number of 0.
+.TP
+.BR -N ", " --name=
+Specify the name of the array to assemble. This must be the name
+that was specified when creating the array.
+
.TP
.BR -f ", " --force
Assemble the array even if some superblocks appear out-of-date
.BR -a ", " "--auto{=no,yes,md,mdp,part}"
See this option under Create and Build options.
+.TP
+.BR -b ", " --bitmap=
+Specify the bitmap file that was given when the array was created.
+
.TP
.BR -U ", " --update=
Update the superblock on each device while assembling the array. The
argument given to this flag can be one of
.BR sparc2.2 ,
.BR summaries ,
+.BR uuid ,
.BR resync ,
+.BR byteorder ,
or
.BR super-minor .
The
.B sparc2.2
-option will adjust the superblock of an array what was created on a Sparc
+option will adjust the superblock of an array what was created on a Sparc
machine running a patched 2.2 Linux kernel. This kernel got the
alignment of part of the superblock wrong. You can use the
.B "--examine --sparc2.2"
assembled. This is not needed on 2.6 and later kernels as they make
this adjustment automatically.
+The
+.B uuid
+option will change the uuid of the array. If a UUID is given with the
+"--uuid" option that UUID will be used as a new UUID and with
+.B NOT
+be used to help identify the devices in the array.
+If no "--uuid" is given, a random uuid is chosen.
+
The
.B resync
option will cause the array to be marked
to perform a "resync" pass to make sure that all redundant information
is correct.
+The
+.B byteorder
+option allows arrays to be moved between machines with different
+byte-order.
+When assembling such an array for the first time after a move, giving
+.B "--update=byteorder"
+will cause
+.I mdadm
+to expect superblocks to have their byteorder reversed, and will
+correct that order before assembling the array. This is only valid
+with original (Verion 0.90) superblocks.
+
The
.B summaries
option will correct the summaries in the superblock. That is the
'''add, or
hotadd listed devices.
+.TP
+.BR --re-add
+Listed devices are assumed to have recently been part of the array,
+and they are re-added. This is only different from --add when a
+write-intent bitmap is present. It causes only those parts of the
+device that have changed since the device was removed from the array
+to be reconstructed.
+
+This flag is only needed with arrays that are built without a
+superblock (i.e. --build, not --create). For array with a superblock,
+.I mdadm
+checks if a superblock is present and automatically determines if a
+re-add is appropriate.
+
.TP
.BR -r ", " --remove
remove listed devices. They must not be active. i.e. they should
.TP
.B --sparc2.2
-In an array was created on a 2.2 Linux kernel patched with RAID
+If an array was created on a 2.2 Linux kernel patched with RAID
support, the superblock will have been created incorrectly, or at
least incompatibly with 2.4 and later kernels. Using the
.B --sparc2.2
.BR -p ", " --program ", " --alert
Give a program to be run whenever an event is detected.
+.TP
+.BR -y ", " --syslog
+Cause all events to be reported through 'syslog'. The messages have
+facility of 'daemon' and varying priorities.
+
.TP
.BR -d ", " --delay
Give a delay in seconds.
.B NewArray
events and more significantly
.B DegradedArray
+and
+.B SparesMissing
events. Running
.in +5
.B " mdadm --monitor --scan -1"
.B TestMessage
alert for every array found at startup. This alert gets mailed and
passed to the alert program. This can be used for testing that alert
-message to get through successfully.
+message do get through successfully.
.SH ASSEMBLE MODE
is not given and insufficient drives were listed to start a complete
(non-degraded) array, then the array is not started (to guard against
usage errors). To insist that the array be started in this case (as
-may work for RAID1, 4, 5 or 6), give the
+may work for RAID1, 4, 5, 6, or 10), give the
.B --run
flag.
files for the first 4 partitions are also created. If a different
number is required it can be simply appended to the auto option.
e.g. "auto=part8". Partition names are created by appending a digit
-string to the device name, with an intervening "_p" if the device name
+string to the device name, with an intervening "p" if the device name
ends with a digit.
The
.PP
This usage is similar to
.BR --create .
-The difference is that it creates a legacy array without a superblock. With
+The difference is that it creates an array without a superblock. With
these arrays there is no difference between initially creating the array and
subsequently assembling the array, except that hopefully there is useful
data there in the second case.
-The level may only be 0, raid0, or linear. All devices must be listed
-and the array will be started once complete.
+The level may raid0, linear, multipath, or faulty, or one of their
+synonyms. All devices must be listed and the array will be started
+once complete.
.SH CREATE MODE
This usage will initialise a new md array, associate some devices with
it, and activate the array.
-This the
+If the
.B --auto
option is given (as described in more detail in the section on
Assemble mode), then the md device will be created with a suitable
may move a spare drive from one array to another if they are in the
same
.B spare-group
-and if the destination array has a failed drive but not spares.
+and if the destination array has a failed drive but no spares.
If any devices are listed on the command line,
.B mdadm
.TP
.B DeviceDisappeared
An md array which previously was configured appears to no longer be
-configured.
+configured. (syslog priority: Critical)
+
+If
+.I mdadm
+was told to monitor an array which is RAID0 or Linear, then it will
+report
+.B DeviceDisappeared
+with the extra information
+.BR Wrong-Level .
+This is because RAID0 and Linear do not support the device-failed,
+hot-spare and resync operations which are monitored.
.TP
.B RebuildStarted
-An md array started reconstruction.
+An md array started reconstruction. (syslog priority: Warning)
.TP
.BI Rebuild NN
Where
.I NN
is 20, 40, 60, or 80, this indicates that rebuild has passed that many
-percentage of the total.
+percentage of the total. (syslog priority: Warning)
.TP
.B RebuildFinished
An md array that was rebuilding, isn't any more, either because it
-finished normally or was aborted.
+finished normally or was aborted. (syslog priority: Warning)
.TP
.B Fail
-An active component device of an array has been marked as faulty.
+An active component device of an array has been marked as
+faulty. (syslog priority: Critical)
.TP
.B FailSpare
A spare component device which was being rebuilt to replace a faulty
-device has failed.
+device has failed. (syslog priority: Critial)
.TP
.B SpareActive
A spare component device which was being rebuilt to replace a faulty
device as been successfully rebuild and has been made active.
+(syslog priority: Info)
.TP
.B NewArray
A new md array has been detected in the
.B /proc/mdstat
-file.
+file. (syslog priority: Info)
.TP
.B DegradedArray
notices a drive failure which causes degradation, but only when
.I mdadm
notices that an array is degraded when it first sees the array.
+(syslog priority: Critial)
.TP
.B MoveSpare
A spare drive has been moved from one array in a
.B spare-group
to another to allow a failed drive to be replaced.
+(syslog priority: Info)
+
+.TP
+.B SparesMissing
+If
+.I mdadm
+has been told, via the config file, that an array should have a certain
+number of spare devices, and
+.I mdadm
+detects that it has fewer that this number when it first sees the
+array, it will report a
+.B SparesMissing
+message.
+(syslog priority: Info)
.TP
.B TestMessage
An array was found at startup, and the
.B --test
flag was given.
+(syslog priority: Info)
.RE
Only
Various types of growth may be added during 2.6 development, possibly
including restructuring a raid5 array to have more active devices.
-Currently the only support available is to change the "size" attribute
-for arrays with redundancy, and the raid-disks attribute of RAID1
-arrays.
+Currently the only support available is to
+.IP \(bu 4
+change the "size" attribute
+for RAID1, RAID5 and RAID6.
+.IP \(bu 4
+change the "raid-disks" attribute of RAID1.
+.IP \(bu 4
+add a write-intent bitmap to a RAID1 array.
+.PP
-Normally when an array is build the "size" it taken from the smallest
+Normally when an array is built the "size" it taken from the smallest
of the drives. If all the small drives in an arrays are, one at a
time, removed and replaced with larger drives, then you could have an
array of large drives with only a small amount used. In this
devices that which were in those slots must be failed and removed.
When the number of devices is increased, any hot spares that are
-present may be activated immediately.
+present will be activated immediately.
+
+A write-intent bitmap can be added to, or remove from, an active RAID1
+array. Either internal bitmap, of bitmaps stored in a separate file
+can be added. Note that if you add a bitmap stored in a file which is
+in a filesystem that is on the raid array being affected, the system
+will deadlock. The bitmap must be on a separate filesystem.
.SH EXAMPLES
.B " mdadm --stop --scan"
.br
This will shut down all array that can be shut down (i.e. are not
-currently in used). This will typically going in a system shutdown script.
+currently in use). This will typically go in a system shutdown script.
.B " mdadm --follow --scan --delay=120"
.br
.BR mdadm.conf (5)
for more details.
+.SH DEVICE NAMES
+
+While entries in the /dev directory can have any format you like,
+.I mdadm
+has an understanding of 'standard' formats which it uses to guide its
+behaviour when creating device files via the
+.I --auto
+option.
+
+The standard names for non-partitioned arrays (the only sort of md
+array available in 2.4 and earlier) either of
+.IP
+/dev/mdNN
+.br
+/dev/md/NN
+.PP
+where NN is a number.
+The standard names for partitionable arrays (as available from 2.6
+onwards) is one of
+.IP
+/dev/md/dNN
+.br
+/dev/md_dNN
+.PP
+Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
.SH NOTE
.B mdadm
was previously known as
.BR mdctl .
-
+.P
+.B mdadm
+is completely separate from the
+.B raidtools
+package, and does not use the
+.I /etc/raidtab
+configuration file at all.
+
.SH SEE ALSO
For information on the various levels of
RAID, check out:
.UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
.UE
+'''.PP
+'''for new releases of the RAID driver check out:
+'''
+'''.IP
+'''.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
+'''ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
+'''.UE
+'''.PP
+'''or
+'''.IP
+'''.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
+'''http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
+'''.UE
.PP
-for new releases of the RAID driver check out:
-
+The lastest version of
+.I mdadm
+should always be available from
.IP
-.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
-ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
+.UR http://www.kernel.org/pub/linux/utils/raid/mdadm/
+http://www.kernel.org/pub/linux/utils/raid/mdadm/
.UE
.PP
-or
-.IP
-.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
-http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
-.URk
-.PP
-.BR mdadm.conf (5),
-.BR md (4).
+.IR mdadm.conf (5),
+.IR md (4).
.PP
.IR raidtab (5),
.IR raid0run (8),
.IR raidstop (8),
-.IR mkraid (8)
+.IR mkraid (8).
projects / thirdparty / mdadm.git / blobdiff