.\" -*- nroff -*-
-''' Copyright Neil Brown and others.
-''' This program is free software; you can redistribute it and/or modify
-''' it under the terms of the GNU General Public License as published by
-''' the Free Software Foundation; either version 2 of the License, or
-''' (at your option) any later version.
-''' See file COPYING in distribution for details.
-.TH MDADM 8 "" v2.6.1
+.\" Copyright Neil Brown and others.
+.\" This program is free software; you can redistribute it and/or modify
+.\" it under the terms of the GNU General Public License as published by
+.\" the Free Software Foundation; either version 2 of the License, or
+.\" (at your option) any later version.
+.\" See file COPYING in distribution for details.
+.TH MDADM 8 "" v3.0-devel2
.SH NAME
mdadm \- manage MD devices
.I aka
-Linux Software Raid.
+Linux Software RAID
.SH SYNOPSIS
.BR RAID6 ,
.BR RAID10 ,
.BR MULTIPATH ,
+.BR FAULTY ,
and
-.BR FAULTY .
+.BR CONTAINER .
.B MULTIPATH
is not a Software RAID mechanism, but does involve
-multiple devices. For
-.B MULTIPATH
+multiple devices:
each device is a path to one common physical storage device.
.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 a different purpose.
+B CONTAINER
+is different again. A
+.B CONTAINER
+is a collection of devices that are
+managed as a set. This is similar to the set of devices connected to
+a hardware RAID controller. The set of devices may contain a number
+of different RAID arrays each utilising some (or all) blocks from a
+number of the devices in the set. For example, two devices in a 5-device set
+might form a RAID1 used the whole devices. The remaining three might
+have a RAID5 over the first half of each device, and a RAID0 over the
+second half.
+
+With a
+.BR CONTAINER ,
+there is one set of metadata that describes all of
+the arrays in the container. So when
+.I mdadm
+creates a
+.B CONTAINER
+device, it just represents the metadata. Other normal arrays (RAID1
+etc) can be created inside that container.
+
+
+.\".I 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
+.\".I mdadm
+.\"and
+.\".B raidtools
+.\"are:
+.\".IP \(bu 4
+.\".I mdadm
+.\"is a single program and not a collection of programs.
+.\".IP \(bu 4
+.\".I mdadm
+.\"can perform (almost) all of its functions without having a
+.\"configuration file and does not use one by default. Also
+.\".I mdadm
+.\"helps with management of the configuration
+.\"file.
+.\".IP \(bu 4
+.\".I 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 a different purpose.
.SH MODES
mdadm has several major modes of operation:
.TP
.B Assemble
-Assemble the parts of a previously created
+Assemble the components of a previously created
array into an active array. Components can be explicitly given
or can be searched for.
-.B mdadm
+.I mdadm
checks that the components
do form a bona fide array, and can, on request, fiddle superblock
information so as to assemble a faulty array.
.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
+components 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
Create a new array with per-device superblocks.
-'''It can progress
-'''in several step create-add-add-run or it can all happen with one command.
+.\"It can progress
+.\"in several step create-add-add-run or it can all happen with one command.
.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, 10 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.
.B "Grow"
Grow (or shrink) an array, or otherwise reshape it in some way.
Currently supported growth options including changing the active size
-of component devices in RAID level 1/4/5/6 and changing the number of
-active devices in RAID1/5/6.
+of component devices and changing the number of active devices in RAID
+levels 1/4/5/6, as well as adding or removing a write-intent bitmap.
.TP
.B "Incremental Assembly"
system. As each device is detected,
.I mdadm
has a chance to include it in some array as appropriate.
+.P
+If a
+.B CONTAINER
+is passed to
+.I mdadm
+in this mode, then any arrays within that container will be assembled
+and started.
.TP
.B Manage
This is an 'everything else' mode that supports operations on active
arrays, operations on component devices such as erasing old superblocks, and
information gathering operations.
-'''This mode allows operations on independent devices such as examine MD
-'''superblocks, erasing old superblocks and stopping active arrays.
+.\"This mode allows operations on independent devices such as examine MD
+.\"superblocks, erasing old superblocks and stopping active arrays.
+.TP
+.B Auto-detect
+This mode does not act on a specific device or array, but rather it
+requests the Linux Kernel to activate any auto-detected arrays.
.SH OPTIONS
.SH Options for selecting a mode are:
Change the size or shape of an active array.
.TP
-.BE \-I ", " \-\-incremental
+.BR \-I ", " \-\-incremental
Add a single device into an appropriate array, and possibly start the array.
+.TP
+.B \-\-auto-detect
+Request that the kernel starts any auto-detected arrays. This can only
+work if
+.I md
+is compiled into the kernel \(em not if it is a module.
+Arrays can be auto-detected by the kernel if all the components are in
+primary MS-DOS partitions with partition type
+.BR FD .
+In-kernel autodetect is not recommended for new installations. Using
+.I mdadm
+to detect and assemble arrays \(em possibly in an
+.I initrd
+\(em is substantially more flexible and should be preferred.
+
.P
If a device is given before any options, or if the first option is
.BR \-\-add ,
.TP
.BR \-h ", " \-\-help
Display general help message or, after one of the above options, a
-mode specific help message.
+mode-specific help message.
.TP
.B \-\-help\-options
.TP
.BR \-q ", " \-\-quiet
Avoid printing purely informative messages. With this,
-.B mdadm
+.I mdadm
will be silent unless there is something really important to report.
.TP
.TP
.BR \-f ", " \-\-force
-Be more forceful about certain operations. See the various modes of
+Be more forceful about certain operations. See the various modes for
the exact meaning of this option in different contexts.
.TP
.BR \-c ", " \-\-config=
Specify the config file. Default is to use
.BR /etc/mdadm.conf ,
-or if that is missing, then
+or if that is missing then
.BR /etc/mdadm/mdadm.conf .
If the config file given is
-.B partitions
+.B "partitions"
then nothing will be read, but
.I mdadm
will act as though the config file contained exactly
-.B "DEVICE partitions"
+.B "DEVICE partitions containers"
and will read
.B /proc/partitions
-to find a list of devices to scan.
+to find a list of devices to scan, and
+.B /proc/mdstat
+to find a list of containers to examine.
If the word
-.B none
+.B "none"
is given for the config file, then
.I mdadm
will act as though the config file were empty.
.TP
.BR \-s ", " \-\-scan
-scan config file or
+Scan config file or
.B /proc/mdstat
for missing information.
In general, this option gives
-.B mdadm
-permission to get any missing information, like component devices,
-array devices, array identities, and alert destination from the
-configuration file:
-.BR /etc/mdadm.conf .
-One exception is MISC mode when using
+.I mdadm
+permission to get any missing information (like component devices,
+array devices, array identities, and alert destination) from the
+configuration file (see previous option);
+one exception is MISC mode when using
.B \-\-detail
or
-.B \-\-stop
+.B \-\-stop,
in which case
.B \-\-scan
says to get a list of array devices from
.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
+28 component 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
+The different sub-versions 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).
+.IP ddf
+Use the "Industry Standard" DDF (Disk Data Format) format. When
+creating a DDF array a
+.B CONTAINER
+will be created, and normal arrays can be created in that container.
+.IP imsm
+Use the Intel Matrix Storage Manager metadata format. This creates a
+.B CONTAINER
+which is managed in a similar manner to DDF.
.RE
.TP
.B \-\-homehost=
This will override any
.B HOMEHOST
-setting in the config file and provides the identify of the host which
+setting in the config file and provides the identity of the host which
should be considered the home for any arrays.
When creating an array, the
.B homehost
will be recorded in the superblock. For version-1 superblocks, it will
-be prefixed to the array name. For version-0.90 superblocks part of
+be prefixed to the array name. For version-0.90 superblocks, part of
the SHA1 hash of the hostname will be stored in the later half of the
UUID.
.TP
.BR \-z ", " \-\-size=
-Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6.
+Amount (in Kibibytes) of space to use from each drive in RAID level 1/4/5/6.
This must be a multiple of the chunk size, and must leave about 128Kb
of space at the end of the drive for the RAID superblock.
If this is not specified
.B max
which means to choose the largest size that fits on all current drives.
+This value can not be used with
+.B CONTAINER
+metadata such as DDF and IMSM.
+
.TP
.BR \-c ", " \-\-chunk=
Specify chunk size of kibibytes. The default is 64.
Set raid level. When used with
.BR \-\-create ,
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
-raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous.
+raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
+Obviously some of these are synonymous.
+
+When a
+.B CONTAINER
+metadata type is requested, only the
+.B container
+level is permitted, and it does not need to be explicitly given.
When used with
.BR \-\-build ,
The default is
.BR left\-symmetric .
-When setting the failure mode for
-.I faulty
+When setting the failure mode for level
+.I faulty,
the options are:
.BR write\-transient ", " wt ,
.BR read\-transient ", " rt ,
.BR read\-fixable ", " rf ,
.BR clear ", " flush ", " none .
-Each mode can be followed by a number which is used as a period
+Each failure mode can be followed by a number, which is used as a period
between fault generation. Without a number, the fault is generated
once on the first relevant request. With a number, the fault will be
-generated after that many request, and will continue to be generated
+generated after that many requests, and will continue to be generated
every time the period elapses.
Multiple failure modes can be current simultaneously by using the
must be specified before the fault mode is specified.
Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
-by a small number. The default is 'n2'.
+by a small number. The default is 'n2'. The supported options are:
-.I n
+.I 'n'
signals 'near' copies. Multiple copies of one data block are at
similar offsets in different devices.
-.I o
+.I 'o'
signals 'offset' copies. Rather than the chunks being duplicated
within a stripe, whole stripes are duplicated but are rotated by one
device so duplicate blocks are on different devices. Thus subsequent
copies of a block are in the next drive, and are one chunk further
down.
-.I f
+.I 'f'
signals 'far' copies
-(multiple copies have very different offsets). See md(4) for more
-detail about 'near' and 'far'.
+(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
.B \-\-force
is also given. The same file should be provided
when assembling the array. If the word
-.B internal
+.B "internal"
is given, then the bitmap is stored with the metadata on the array,
and so is replicated on all devices. If the word
-.B none
+.B "none"
is given with
.B \-\-grow
mode, then any bitmap that is present is removed.
Set the chunksize of the bitmap. Each bit corresponds to that many
Kilobytes of storage.
When using a file based bitmap, the default is to use the smallest
-size that is atleast 4 and requires no more than 2^21 chunks.
+size that is at-least 4 and requires no more than 2^21 chunks.
When using an
.B internal
bitmap, the chunksize is automatically determined to make best use of
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 \(em while normally safe \(em is not
-recommended. Use this ony if you really know what you are doing.
+recommended. Use this only if you really know what you are doing.
.TP
.BR \-\-backup\-file=
end of this option (e.g.
.BR \-\-auto=p7 ).
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
+and a number, e.g. "/dev/md/home1p3". If there is no
trailing digit, then the partition names just have a number added,
-e.g. "/dev/scratch3".
+e.g. "/dev/md/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
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.
-
-.TP
-.BR \-\-symlink = no
-Normally when
-.B \-\-auto
-causes
-.I mdadm
-to create devices in
-.B /dev/md/
-it will also create symlinks from
-.B /dev/
-with names starting with
-.B md
-or
-.BR md_ .
-Use
-.B \-\-symlink=no
-to suppress this, or
-.B \-\-symlink=yes
-to enforce this even if it is suppressing
-.IR mdadm.conf .
-
+non-standard name. Name that are not in 'standard' format are only
+allowed in "/dev/md/".
+
+\".TP
+\".BR \-\-symlink = no
+\"Normally when
+\".B \-\-auto
+\"causes
+\".I mdadm
+\"to create devices in
+\".B /dev/md/
+\"it will also create symlinks from
+\".B /dev/
+\"with names starting with
+\".B md
+\"or
+\".BR md_ .
+\"Use
+\".B \-\-symlink=no
+\"to suppress this, or
+\".B \-\-symlink=yes
+\"to enforce this even if it is suppressing
+\".IR mdadm.conf .
+\"
.SH For assemble:
to use the minor number of the md device that is being assembled.
e.g. when assembling
.BR /dev/md0 ,
-.M \-\-super\-minor=dev
+.B \-\-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. It must either match
-then name stored in the superblock exactly, or it must match
+the name stored in the superblock exactly, or it must match
with the current
.I homehost
-is added to the start of the given name.
+prefixed to the start of the given name.
.TP
.BR \-f ", " \-\-force
.B \-\-no\-degraded
This is the reverse of
.B \-\-run
-in that it inhibits the started if array unless all expected drives
+in that it inhibits the startup of array unless all expected drives
are present. This is only needed with
-.B \-\-scan
-and can be used if you physical connections to devices are
+.B \-\-scan,
+and can be used if the physical connections to devices are
not as reliable as you would like.
.TP
.TP
.B \-\-auto\-update\-homehost
-This flag is only meaning with auto-assembly (see discussion below).
+This flag is only meaningful with auto-assembly (see discussion below).
In that situation, if no suitable arrays are found for this homehost,
.I mdadm
-will recan for any arrays at all and will assemble them and update the
+will rescan for any arrays at all and will assemble them and update the
homehost to match the current host.
.SH For Manage mode:
can be given to
.BR \-\-remove .
The first causes all failed device to be removed. The second causes
-any device which is no longer connected to the system (i.e and open
+any device which is no longer connected to the system (i.e an 'open'
returns
.BR ENXIO )
to be removed. This will only succeed for devices that are spares or
same as
.BR \-\-fail .
+.TP
+.BR \-\-write\-mostly
+Subsequent devices that are added or re-added will have the 'write-mostly'
+flag set. This is only valid for RAID! and means that the 'md' driver
+will avoid reading from these devices if possible.
+.TP
+.BR \-\-readwrite
+Subsequent devices that are added or re-added will have the 'write-mostly'
+flag cleared.
+
+
.P
-Each of these options require that the first device list is the array
-to be acted upon and the remainder are component devices to be added,
-removed, or marked as fault. Several different operations can be
+Each of these options require that the first device listed is the array
+to be acted upon, and the remainder are component devices to be added,
+removed, or marked as faulty. Several different operations can be
specified for different devices, e.g.
.in +5
mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
.in -5
Each operation applies to all devices listed until the next
-operations.
+operation.
If an array is using a write-intent bitmap, then devices which have
been removed can be re-added in a way that avoids a full
-reconstruction but instead just updated the blocks that have changed
+reconstruction but instead just updates the blocks that have changed
since the device was removed. For arrays with persistent metadata
(superblocks) this is done automatically. For arrays created with
.B \-\-build
.BR \-\-re\-add .
Devices can only be removed from an array if they are not in active
-use. i.e. that must be spares or failed devices. To remove an active
-device, it must be marked as
-.B faulty
-first.
+use, i.e. that must be spares or failed devices. To remove an active
+device, it must first be marked as
+.B faulty.
.SH For Misc mode:
.TP
.BR \-Y ", " \-\-export
When used with
-.BR \-\-detail ,
+.B \-\-detail
+or
+.BR \-\-examine ,
output will be formatted as
.B key=value
pairs for easy import into the environment.
.TP
.BR \-X ", " \-\-examine\-bitmap
Report information about a bitmap file.
+The argument is either an external bitmap file or an array component
+in case of an internal bitmap.
.TP
.BR \-R ", " \-\-run
will return with success if it actually waited for every device
listed, otherwise it will return failure.
+.TP
+.BR \-\-wait\-clean
+For each md device given, arrange for the array to be marked clean as
+soon as possible. Also, quiesce resync so that the monitor for external
+metadata arrays (mdmon) has an opportunity to checkpoint the resync
+position.
+.I mdadm
+will return with success if the array uses external metadata and we
+successfully waited. For native arrays this returns immediately as the
+kernel handles both dirty-clean transitions and resync checkpointing in
+the kernel at shutdown. No action is taken if safe-mode handling is
+disabled.
+
.SH For Incremental Assembly mode:
.TP
.BR \-\-rebuild\-map ", " \-r
.TP
.BR \-d ", " \-\-delay
Give a delay in seconds.
-.B mdadm
+.I mdadm
polls the md arrays and then waits this many seconds before polling
again. The default is 60 seconds.
.TP
.BR \-f ", " \-\-daemonise
Tell
-.B mdadm
+.I mdadm
to run as a background daemon if it decides to monitor anything. This
causes it to fork and run in the child, and to disconnect form the
terminal. The process id of the child is written to stdout.
.TP
.BR \-i ", " \-\-pid\-file
When
-.B mdadm
+.I mdadm
is running in daemon mode, write the pid of the daemon process to
the specified file, instead of printing it on standard output.
In the second usage example, all devices listed are treated as md
devices and assembly is attempted.
In the third (where no devices are listed) all md devices that are
-listed in the configuration file are assembled.
+listed in the configuration file are assembled. Then any arrays that
+can be found on unused devices will also be assembled.
If precisely one device is listed, but
.B \-\-scan
.I mdadm
acts as though
.B \-\-scan
-was given and identify information is extracted from the configuration file.
+was given and identity information is extracted from the configuration file.
The identity can be given with the
.B \-\-uuid
option, with the
.B \-\-super\-minor
-option, can be found in the config file, or will be taken from the
-super block on the first component-device listed on the command line.
+option, will be taken from the md-device record in the config file, or
+will be taken from the super block of the first component-device
+listed on the command line.
Devices can be given on the
.B \-\-assemble
.BR \-\-scan .
In the later case,
.B /etc/mdadm.conf
+or
+.B /etc/mdadm/mdadm.conf
is used.
If
.B \-\-auto
option must be given to clarify how and whether the device should be
created.
-
This can be useful for handling partitioned devices (which don't have
a stable device number \(em it can change after a reboot) and when using
"udev" to manage your
If the option to "auto" is "mdp" or "part" or (on the command line
only) "p", then mdadm will create a partitionable array, using the
-first free one that is not in use, and does not already have an entry
+first free one that is not in use and does not already have an entry
in /dev (apart from numeric /dev/md* entries).
If the option to "auto" is "yes" or "md" or (on the command line)
device entries with meaningful names such as "/dev/md/home" or
"/dev/md/root", rather than names based on the numerical array number.
-When using this option to create a partitionable array, the device
+When using option "auto" to create a partitionable array, the device
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
will first attempt to assemble all the arrays listed in the config
file.
-If a
-.B homehost
-has been specified (either in the config file or on the command line),
-.I mdadm
-will look further for possible arrays and will try to assemble
-anything that it finds which is tagged as belonging to the given
-homehost. This is the only situation where
-.I mdadm
-will assemble arrays without being given specific device name or
-identify information for the array.
+It will then look further for possible arrays and will try to assemble
+anything that it finds. Arrays which are tagged as belonging to the given
+homehost will be assembled and started normally. Arrays which do not
+obviously belong to this host are given names that are expected not to
+conflict with anything local, and are started "read-auto" so that
+nothing is written to any device until the array is written to. i.e.
+automatic resync etc is delayed.
If
.I mdadm
If the array uses version-1 metadata, then the
.B name
from the superblock is used to similarly create a name in
-.BR /dev/md .
-The name will have any 'host' prefix stripped first.
+.BR /dev/md
+(the name will have any 'host' prefix stripped first).
If
.I mdadm
.HP 12
Usage:
.B mdadm \-\-build
-.I device
+.I md-device
.BI \-\-chunk= X
.BI \-\-level= Y
.BI \-\-raid\-devices= Z
.HP 12
Usage:
.B mdadm \-\-create
-.I device
+.I md-device
.BI \-\-chunk= X
.BI \-\-level= Y
.br
To create a "degraded" array in which some devices are missing, simply
give the word "\fBmissing\fP"
in place of a device name. This will cause
-.B mdadm
+.I mdadm
to leave the corresponding slot in the array empty.
For a RAID4 or RAID5 array at most one slot can be
"\fBmissing\fP"; for a RAID6 array at most two slots.
"\fBmissing\fP".
When creating a RAID5 array,
-.B mdadm
+.I mdadm
will automatically create a degraded array with an extra spare drive.
This is because building the spare into a degraded array is in general faster than resyncing
the parity on a non-degraded, but not clean, array. This feature can
.B \-\-force
option.
-When creating an array with version-1 metadata a name for the host is
+When creating an array with version-1 metadata a name for the array is
required.
If this is not given with the
.B \-\-name
option,
.I mdadm
-will chose a name based on the last component of the name of the
+will choose a name based on the last component of the name of the
device being created. So if
.B /dev/md3
is being created, then the name
.B home
will be used.
+When creating a partition based array, using
+.I mdadm
+with version-1.x metadata, the partition type should be set to
+.B 0xDA
+(non fs-data). This type selection allows for greater precision since
+using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
+might create problems in the event of array recovery through a live cdrom.
+
A new array will normally get a randomly assigned 128bit UUID which is
very likely to be unique. If you have a specific need, you can choose
a UUID for the array by giving the
when creating a v0.90 array will silently override any
.B \-\-homehost=
setting.
-'''If the
-'''.B \-\-size
-'''option is given, it is not necessary to list any component-devices in this command.
-'''They can be added later, before a
-'''.B \-\-run.
-'''If no
-'''.B \-\-size
-'''is given, the apparent size of the smallest drive given is used.
+.\"If the
+.\".B \-\-size
+.\"option is given, it is not necessary to list any component-devices in this command.
+.\"They can be added later, before a
+.\".B \-\-run.
+.\"If no
+.\".B \-\-size
+.\"is given, the apparent size of the smallest drive given is used.
+
+When creating an array within a
+.B CONTAINER
+.I mdadm
+can be given either the list of devices to use, or simply the name of
+the container. The former case gives control over which devices in
+the container will be used for the array. The latter case allows
+.I mdadm
+to automatically choose which devices to use based on how much spare
+space is available.
The General Management options that are valid with
.B \-\-create
MISC mode includes a number of distinct operations that
operate on distinct devices. The operations are:
.TP
-\-\-query
+.B \-\-query
The device is examined to see if it is
(1) an active md array, or
(2) a component of an md array.
The information discovered is reported.
.TP
-\-\-detail
+.B \-\-detail
The device should be an active md device.
.B mdadm
will display a detailed description of the array.
.I mdadm
will normally be 0 unless
.I mdadm
-failed to get useful information about the device(s). However if the
+failed to get useful information about the device(s); however, if the
.B \-\-test
option is given, then the exit status will be:
.RS
The array has at least one failed device.
.TP
2
-The array has multiple failed devices and hence is unusable (raid4 or
-raid5).
+The array has multiple failed devices such that it is unusable.
.TP
4
There was an error while trying to get information about the device.
.RE
.TP
-\-\-examine
+.B \-\-examine
The device should be a component of an md array.
-.B mdadm
+.I mdadm
will read the md superblock of the device and display the contents.
If
.B \-\-brief
-is given, or
+or
.B \-\-scan
-then multiple devices that are components of the one array
+is given, then multiple devices that are components of the one array
are grouped together and reported in a single entry suitable
for inclusion in
.BR /etc/mdadm.conf .
config file to be examined.
.TP
-\-\-stop
+.B \-\-stop
The devices should be active md arrays which will be deactivated, as
long as they are not currently in use.
.TP
-\-\-run
+.B \-\-run
This will fully activate a partially assembled md array.
.TP
-\-\-readonly
+.B \-\-readonly
This will mark an active array as read-only, providing that it is
not currently being used.
.TP
-\-\-readwrite
+.B \-\-readwrite
This will change a
.B readonly
array back to being read/write.
.TP
-\-\-scan
+.B \-\-scan
For all operations except
.BR \-\-examine ,
.B \-\-scan
.PP
This usage causes
-.B mdadm
+.I mdadm
to periodically poll a number of md arrays and to report on any events
noticed.
-.B mdadm
+.I mdadm
will never exit once it decides that there are arrays to be checked,
so it should normally be run in the background.
As well as reporting events,
-.B mdadm
+.I mdadm
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 no spares.
If any devices are listed on the command line,
-.B mdadm
+.I mdadm
will only monitor those devices. Otherwise all arrays listed in the
configuration file will be monitored. Further, if
.B \-\-scan
These events are passed to a separate program (if specified) and may
be mailed to a given E-mail address.
-When passing event to program, the program is run once for each event
-and is given 2 or 3 command-line arguments. The first is the
-name of the event (see below). The second is the name of the
+When passing events to a program, the program is run once for each event,
+and is given 2 or 3 command-line arguments: the first is the
+name of the event (see below), the second is the name of the
md device which is affected, and the third is the name of a related
-device if relevant, such as a component device that has failed.
+device if relevant (such as a component device that has failed).
If
.B \-\-scan
is given, then a program or an E-mail address must be specified on the
command line or in the config file. If neither are available, then
-.B mdadm
+.I mdadm
will not monitor anything.
Without
-.B \-\-scan
-.B mdadm
+.B \-\-scan,
+.I mdadm
will continue monitoring as long as something was found to monitor. If
no program or email is given, then each event is reported to
.BR stdout .
.TP
.B FailSpare
A spare component device which was being rebuilt to replace a faulty
-device has failed. (syslog priority: Critial)
+device has failed. (syslog priority: Critical)
.TP
.B SpareActive
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)
+(syslog priority: Critical)
.TP
.B MoveSpare
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
+detects that it has fewer than this number when it first sees the
array, it will report a
.B SparesMissing
message.
.RE
Only
-.B Fail ,
-.B FailSpare ,
-.B DegradedArray ,
-.B SparesMissing ,
+.B Fail,
+.B FailSpare,
+.B DegradedArray,
+.B SparesMissing
and
.B TestMessage
cause Email to be sent. All events cause the program to be run.
-The program is run with two or three arguments, they being the event
+The program is run with two or three arguments: the event
name, the array device and possibly a second device.
Each event has an associated array device (e.g.
the second device is the array that the spare was moved from.
For
-.B mdadm
+.I mdadm
to move spares from one array to another, the different arrays need to
-be labelled with the same
+be labeled with the same
.B spare-group
in the configuration file. The
.B spare-group
-name can be any string. It is only necessary that different spare
+name can be any string; it is only necessary that different spare
groups use different names.
When
-.B mdadm
-detects that an array which is in a spare group has fewer active
+.I mdadm
+detects that an array in a spare group has fewer active
devices than necessary for the complete array, and has no spare
devices, it will look for another array in the same spare group that
has a full complement of working drive and a spare. It will then
change the "size" attribute
for RAID1, RAID5 and RAID6.
.IP \(bu 4
-increase the "raid-disks" attribute of RAID1, RAID5, and RAID6.
+increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6.
.IP \(bu 4
-add a write-intent bitmap to any array which support these bitmaps, or
+add a write-intent bitmap to any array which supports these bitmaps, or
remove a write-intent bitmap from such an array.
.PP
+GROW mode is not currently supported for
+.B CONTAINERS
+or arrays inside containers.
+
.SS SIZE CHANGES
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
When reducing the number of devices in a RAID1 array, the slots which
are to be removed from the array must already be vacant. That is, the
-devices that which were in those slots must be failed and removed.
+devices which were in those slots must be failed and removed.
When the number of devices is increased, any hot spares that are
present will be activated immediately.
.SS BITMAP CHANGES
A write-intent bitmap can be added to, or removed from, an active
-array. Either internal bitmaps, or bitmaps stored in a separate file
+array. Either internal bitmaps, or 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.
.B "mdadm \-\-incremental"
to be conditionally added to an appropriate array.
+If the device passed is a
+.B CONTAINER
+device created by a previous call to
+.IR mdadm ,
+then rather than trying to add that device to an array, all the arrays
+described by the metadata of the container will be started.
+
.I mdadm
performs a number of tests to determine if the device is part of an
-array, and which array is should be part of. If an appropriate array
+array, and which array it should be part of. If an appropriate array
is found, or can be created,
.I mdadm
adds the device to the array and conditionally starts the array.
(active or spare) parts of that array. It does not currently support
automatic inclusion of a new drive as a spare in some array.
-.B "mdadm \-\-incremental"
-requires a bug present in all kernels through 2.6.19, to be fixed.
-Hopefully this will be fixed in 2.6.20. Alternately apply the patch
-which is included with the mdadm source distribution. If
-.I mdadm
-detects that this bug is present, it will abort any attempt to use
-.BR \-\-incremental .
-
The tests that
.I mdadm
makes are as follow:
in
.B mdadm.conf
which identifies the array (either by UUID, by name, by device list,
-or by minor-number), the array was created with a
+or by minor-number), or the array was created with a
.B homehost
-specified, and that
+specified and that
.B homehost
-matches that which is given in
+matches the one in
.B mdadm.conf
or on the command line.
If
.IP +
.I mdadm
-keeps a list of arrays that is has partly assembled in
+keeps a list of arrays that it has partially assembled in
.B /var/run/mdadm/map
(or
.B /var/run/mdadm.map
As an alternative,
.B \-\-run
may be passed to
-.B mdadm
+.I mdadm
in which case the array will be run as soon as there are enough
devices present for the data to be accessible. For a raid1, that
means one device will start the array. For a clean raid5, the array
will be started as soon as all but one drive is present.
-Note that neither of these approaches is really ideal. If it is can
+Note that neither of these approaches is really ideal. If it can
be known that all device discovery has completed, then
.br
.B " mdadm \-IRs"
happens. Further devices that are found before the first write can
still be added safely.
+
+.SH ENVIRONMENT
+This section describes environment variables that affect how mdadm
+operates.
+
+.TP
+.B MDADM_NO_MDMON
+Setting this value to 1 will prevent mdadm from automatically launching
+mdmon. This variable is intended primarily for debugging mdadm/mdmon.
+
+.TP
+.B MDADM_NO_UDEV
+Normally,
+.I mdadm
+does not create any device nodes in /dev, but leaves that task to
+.IR udev .
+If
+.I udev
+appears not to be configured, or if this environment variable is set
+to '1', the
+.I mdadm
+will create and devices that are needed.
+
.SH EXAMPLES
.B " mdadm \-\-query /dev/name-of-device"
.B " mdadm \-\-assemble \-\-scan"
.br
-This will assemble and start all arrays listed in the standard config file
+This will assemble and start all arrays listed in the standard config
file. This command will typically go in a system startup file.
.B " mdadm \-\-stop \-\-scan"
.br
-This will shut down all array that can be shut down (i.e. are not
+This will shut down all arrays that can be shut down (i.e. are not
currently in use). This will typically go in a system shutdown script.
.B " mdadm \-\-follow \-\-scan \-\-delay=120"
.B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
.br
.B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
-.ber
-This will find what arrays could be assembled from existing IDE and
-SCSI whole drives (not partitions) and store the information is the
+.br
+This will find arrays which could be assembled from existing IDE and
+SCSI whole drives (not partitions), and store the information in the
format of a config file.
This file is very likely to contain unwanted detail, particularly
the
Create a list of devices by reading
.BR /proc/partitions ,
scan these for RAID superblocks, and printout a brief listing of all
-that was found.
+that were found.
.B " mdadm \-Ac partitions \-m 0 /dev/md0"
.br
Any devices which are components of /dev/md4 will be marked as faulty
and then remove from the array.
+.B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
+.br
+Create a DDF array over 6 devices.
+
+.B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
+.br
+Create a raid5 array over any 3 devices in the given DDF set. Use
+only 30 gigabytes of each device.
+
+.B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
+.br
+Assemble a pre-exist ddf array.
+
+.B " mdadm -I /dev/md/ddf1"
+.br
+Assemble all arrays contained in the ddf array, assigning names as
+appropriate.
+
.B " mdadm \-\-create \-\-help"
.br
Provide help about the Create mode.
filesystem,
.B /proc/mdstat
lists all active md devices with information about them.
-.B mdadm
+.I mdadm
uses this to find arrays when
.B \-\-scan
is given in Misc mode, and to monitor array reconstruction
.SS /var/run/mdadm/map
When
.B \-\-incremental
-mode is used. this file gets a list of arrays currently being created.
+mode is used, this file gets a list of arrays currently being created.
If
.B /var/run/mdadm
does not exist as a directory, then
.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
-.B \-\-auto
-option.
+understand two sorts of names for array devices.
+
+The first is the so-called 'standard' format name, which matches the
+names used by the kernel and which appear in
+.IR /proc/mdstat .
+
+The second sort can be freely chosen, but must reside in
+.IR /dev/md/ .
+When giving a device name to
+.I mdadm
+to create or assemble an array, either full path name such as
+.I /dev/md0
+or
+.I /dev/md/home
+can be given, or just the suffix of the second sort of name, such as
+.I home
+can be given.
+
+When
+.I mdadm
+chooses device names during auto-assembly, it will normally add a
+small sequence number to the end of the name to avoid conflicted
+between multiple arrays that have the same name. If
+.I mdadm
+can reasonably determine that the array really is meant for this host,
+either by a hostname in the metadata, or by the presence of the array
+in /etc/mdadm.conf, then it will leave of the suffix if possible.
The standard names for non-partitioned arrays (the only sort of md
-array available in 2.4 and earlier) either of
+array available in 2.4 and earlier) are of the form
.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
+onwards) are of the form
.IP
-/dev/md/dNN
-.br
/dev/md_dNN
.PP
Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
+.PP
+From kernel version, 2.6.28 the "non-partitioned array" can actually
+be partitioned. So the "md_dNN" names are no longer needed, and
+partitions such as "/dev/mdNNpXX" are possible.
.SH NOTE
-.B mdadm
+.I mdadm
was previously known as
-.BR mdctl .
+.IR mdctl .
.P
-.B mdadm
+.I mdadm
is completely separate from the
-.B raidtools
+.I 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:
-
+For further information on mdadm usage, MD and the various levels of
+RAID, see:
.IP
-.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
+.B http://linux\-raid.osdl.org/
+.PP
+(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
+.\".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
The latest version of
.I mdadm
should always be available from
.IP
-.UR http://www.kernel.org/pub/linux/utils/raid/mdadm/
-http://www.kernel.org/pub/linux/utils/raid/mdadm/
-.UE
+.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
+.PP
+Related man pages:
.PP
.IR mdadm.conf (5),
.IR md (4).
projects / thirdparty / mdadm.git / blobdiff