.B Misc
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.
+information-gathering operations.
.\"This mode allows operations on independent devices such as examine MD
.\"superblocks, erasing old superblocks and stopping active arrays.
.TP
.BR \-h ", " \-\-help
-Display general help message or, after one of the above options, a
+Display a general help message or, after one of the above options, a
mode-specific help message.
.TP
.B \-\-help\-options
-Display more detailed help about command line parsing and some commonly
+Display more detailed help about command-line parsing and some commonly
used options.
.TP
.TP
.BR \-c ", " \-\-config=
-Specify the config file or directory. If not specified, default config file
+Specify the config file or directory. If not specified, the default config file
and default conf.d directory will be used. See
.BR mdadm.conf (5)
for more details.
.B homehost
will be recorded in the metadata. For version-1 superblocks, it will
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
+the SHA1 hash of the hostname will be stored in the latter half of the
UUID.
When reporting information about an array, any array which is tagged
When using Auto-Assemble, only arrays tagged for the given homehost
will be allowed to use 'local' names (i.e. not ending in '_' followed
by a digit string). See below under
-.BR "Auto Assembly" .
+.BR "Auto-Assembly" .
The special name "\fBany\fP" can be used as a wild card. If an array
is created with
.I mdadm
needs to print the name for a device it normally finds the name in
.B /dev
-which refers to the device and is shortest. When a path component is
+which refers to the device and is the shortest. When a path component is
given with
.B \-\-prefer
.I mdadm
This option can be used with
.B \-\-create
-for determining initial size of an array. For external metadata,
+for determining the initial size of an array. For external metadata,
it can be used on a volume, but not on a container itself.
-Setting initial size of
+Setting the initial size of
.B RAID 0
array is only valid for external metadata.
.TP
.BR \-c ", " \-\-chunk=
-Specify chunk size of kilobytes. The default when creating an
+Specify chunk size in kilobytes. The default when creating an
array is 512KB. To ensure compatibility with earlier versions, the
default when building an array with no persistent metadata is 64KB.
This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power
-of 2. In any case it must be a multiple of 4KB.
+of 2, with minimal chunk size being 4KB.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
Megabytes, Gigabytes or Terabytes respectively.
.TP
.BR \-\-rounding=
-Specify rounding factor for a Linear array. The size of each
+Specify the rounding factor for a Linear array. The size of each
component will be rounded down to a multiple of this size.
This is a synonym for
.B \-\-chunk
and "flush" will clear any persistent faults.
The layout options for RAID10 are one of 'n', 'o' or 'f' followed
-by a small number. The default is 'n2'. The supported options are:
+by a small number signifying the number of copies of each datablock.
+The default is 'n2'. The supported options are:
.I 'n'
signals 'near' copies. Multiple copies of one data block are at
(multiple copies have very different offsets).
See md(4) for more detail about 'near', 'offset', and 'far'.
-The number is the number of copies of each datablock. 2 is normal, 3
+As for the number of copies of each data block, 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
started using a different layout. This could lead to
data corruption. Since Linux 5.4 (and various stable releases that received
backports), the kernel will not accept such an array unless
-a layout is explictly set. It can be set to
+a layout is explicitly set. It can be set to
.RB ' original '
or
.RB ' alternate '.
.TP
.BR \-\-bitmap\-chunk=
-Set the chunksize of the bitmap. Each bit corresponds to that many
+Set the chunk size 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 at-least 4 and requires no more than 2^21 chunks.
+When using a file-based bitmap, the default is to use the smallest
+size that is at least 4 and requires no more than 2^21 chunks.
When using an
.B internal
-bitmap, the chunksize defaults to 64Meg, or larger if necessary to
+bitmap, the chunk size defaults to 64Meg, or larger if necessary to
fit the bitmap into the available space.
A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
.BR \-\-backup\-file=
This is needed when
.B \-\-grow
-is used to increase the number of raid-devices in a RAID5 or RAID6 if
+is used to increase the number of raid devices in a RAID5 or RAID6 if
there are no spare devices available, or to shrink, change RAID level
or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
The file must be stored on a separate device, not on the RAID array
.B \-\-data\-offset
can be specified as
.BR variable .
-In the case each member device is expected to have a offset appended
+In the case each member device is expected to have an offset appended
to the name, separated by a colon. This makes it possible to recreate
exactly an array which has varying data offsets (as can happen when
different versions of
.I mdadm
accept the geometry and layout specified without question. Normally
.I mdadm
-will not allow creation of an array with only one device, and will try
+will not allow the creation of an array with only one device, and will try
to create a RAID5 array with one missing drive (as this makes the
initial resync work faster). With
.BR \-\-force ,
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
device number based on that name. If the device name is not in one of these
-formats, then a unused device number will be allocated. The device
+formats, then an unused device number will be allocated. The device
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. Names that are not in 'standard' format are only
.B \-\-add
can be used to add some extra devices to be included in the array.
In most cases this is not needed as the extra devices can be added as
-spares first, and then the number of raid-disks can be changed.
-However for RAID0, it is not possible to add spares. So to increase
+spares first, and then the number of raid disks can be changed.
+However, for RAID0 it is not possible to add spares. So to increase
the number of devices in a RAID0, it is necessary to set the new
number of devices, and to add the new devices, in the same command.
.TP
.BR \-\-nodes
-Only works when the array is for clustered environment. It specifies
+Only works when the array is created for a clustered environment. It specifies
the maximum number of nodes in the cluster that will use this device
simultaneously. If not specified, this defaults to 4.
.TP
.BR \-\-write-journal
Specify journal device for the RAID-4/5/6 array. The journal device
-should be a SSD with reasonable lifetime.
+should be an SSD with a reasonable lifetime.
.TP
.BR \-k ", " \-\-consistency\-policy=
-Specify how the array maintains consistency in case of unexpected shutdown.
+Specify how the array maintains consistency in the case of an unexpected shutdown.
Only relevant for RAID levels with redundancy.
Currently supported options are:
.RS
.TP
.B resync
Full resync is performed and all redundancy is regenerated when the array is
-started after unclean shutdown.
+started after an unclean shutdown.
.TP
.B bitmap
.TP
.B journal
-For RAID levels 4/5/6, journal device is used to log transactions and replay
-after unclean shutdown. Implicitly selected when using
+For RAID levels 4/5/6, the journal device is used to log transactions and replay
+after an unclean shutdown. Implicitly selected when using
.BR \-\-write\-journal .
.TP
reports a different "Preferred Minor" to
.BR \-\-detail .
In some cases this update will be performed automatically
-by the kernel driver. In particular the update happens automatically
+by the kernel driver. In particular, the update happens automatically
at the first write to an array with redundancy (RAID level 1 or
greater) on a 2.6 (or later) kernel.
The
.B home\-cluster
option will change the cluster name as recorded in the superblock and
-bitmap. This option only works for clustered environment.
+bitmap. This option only works for a clustered environment.
The
.B resync
.TP
.BR \-\-freeze\-reshape
-Option is intended to be used in start-up scripts during initrd boot phase.
-When array under reshape is assembled during initrd phase, this option
-stops reshape after reshape critical section is being restored. This happens
-before file system pivot operation and avoids loss of file system context.
+This option is intended to be used in start-up scripts during the initrd boot phase.
+When the array under reshape is assembled during the initrd phase, this option
+stops the reshape after the reshape-critical section has been restored. This happens
+before the file system pivot operation and avoids loss of filesystem context.
Losing file system context would cause reshape to be broken.
Reshape can be continued later using the
If the metadata on the device reports that it is a member of the
array, and the slot that it used is still vacant, then the device will
be added back to the array in the same position. This will normally
-cause the data for that device to be recovered. However based on the
+cause the data for that device to be recovered. However, based on the
event count on the device, the recovery may only require sections that
-are flagged a write-intent bitmap to be recovered or may not require
+are flagged by a write-intent bitmap to be recovered or may not require
any recovery at all.
When used on an array that has no metadata (i.e. it was built with
it will be assumed that bitmap-based recovery is enough to make the
device fully consistent with the array.
-When used with v1.x metadata,
.B \-\-re\-add
-can be accompanied by
+can also be accompanied by
.BR \-\-update=devicesize ,
.BR \-\-update=bbl ", or"
.BR \-\-update=no\-bbl .
-See the description of these option when used in Assemble mode for an
+See descriptions of these options when used in Assemble mode for an
explanation of their use.
If the device name given is
except that it does not attempt
.B \-\-re\-add
first. The device will be added as a spare even if it looks like it
-could be an recent member of the array.
+could be a recent member of the array.
.TP
.BR \-r ", " \-\-remove
.B set-A
can be given to
.BR \-\-remove .
-The first causes all failed device to be removed. The second causes
+The first causes all failed devices to be removed. The second causes
any device which is no longer connected to the system (i.e an 'open'
returns
.BR ENXIO )
to be removed.
-The third will remove a set as describe below under
+The third will remove a set as described below under
.BR \-\-fail .
.TP
of devices, the devices can be conceptually divided into sets where
each set contains a single complete copy of the data on the array.
Sometimes a RAID10 array will be configured so that these sets are on
-separate controllers. In this case all the devices in one set can be
+separate controllers. In this case, all the devices in one set can be
failed by giving a name like
.B set\-A
or
.B \-\-replace
devices. The devices listed after
.B \-\-with
-will be preferentially used to replace the devices listed after
+will preferentially be used to replace the devices listed after
.BR \-\-replace .
-These device must already be spare devices in the array.
+These devices must already be spare devices in the array.
.TP
.BR \-\-write\-mostly
.TP
.BR \-\-add-journal
-Add journal to an existing array, or recreate journal for RAID-4/5/6 array
-that lost a journal device. To avoid interrupting on-going write opertions,
+Add a journal to an existing array, or recreate journal for a RAID-4/5/6 array
+that lost a journal device. To avoid interrupting ongoing write operations,
.B \-\-add-journal
only works for array in Read-Only state.
.TP
.BR \-\-detail\-platform
Print details of the platform's RAID capabilities (firmware / hardware
-topology) for a given metadata format. If used without argument, mdadm
+topology) for a given metadata format. If used without an argument, mdadm
will scan all controllers looking for their capabilities. Otherwise, mdadm
-will only look at the controller specified by the argument in form of an
+will only look at the controller specified by the argument in the form of an
absolute filepath or a link, e.g.
.IR /sys/devices/pci0000:00/0000:00:1f.2 .
doesn't appear to be valid.
.B Note:
-Be careful to call \-\-zero\-superblock with clustered raid, make sure
-array isn't used or assembled in other cluster node before execute it.
+Be careful when calling \-\-zero\-superblock with clustered raid. Make sure
+the array isn't used or assembled in another cluster node before executing it.
.TP
.B \-\-kill\-subarray=
is given, arrange for the array to be marked clean as soon as possible.
.I mdadm
will return with success if the array uses external metadata and we
-successfully waited. For native arrays this returns immediately as the
+successfully waited. For native arrays, this returns immediately as the
kernel handles dirty-clean transitions at shutdown. No action is taken
if safe-mode handling is disabled.
.TP
.BR \-\-run ", " \-R
-Run any array assembled as soon as a minimal number of devices are
+Run any array assembled as soon as a minimal number of devices is
available, rather than waiting until all expected devices are present.
.TP
a new device appears at the same location it can be automatically
added to the same array. This allows the failed device to be
automatically replaced by a new device without metadata if it appears
-at specified path. This option is normally only set by a
+at specified path. This option is normally only set by an
.I udev
script.
.PP
This usage assembles one or more RAID arrays from pre-existing components.
For each array, mdadm needs to know the md device, the identity of the
-array, and a number of component-devices. These can be found in a number of ways.
+array, and the number of component devices. These can be found in a number of ways.
In the first usage example (without the
.BR \-\-scan )
.B \-\-config
or requested with (a possibly implicit)
.BR \-\-scan .
-In the later case, default config file is used. See
+In the latter case, the default config file is used. See
.BR mdadm.conf (5)
for more details.
.B /dev
itself.
-In Linux kernels prior to version 2.6.28 there were two distinctly
-different types of md devices that could be created: one that could be
+In Linux kernels prior to version 2.6.28 there were two distinct
+types of md devices that could be created: one that could be
partitioned using standard partitioning tools and one that could not.
-Since 2.6.28 that distinction is no longer relevant as both type of
+Since 2.6.28 that distinction is no longer relevant as both types of
devices can be partitioned.
.I mdadm
will normally create the type that originally could not be partitioned
-as it has a well defined major number (9).
+as it has a well-defined major number (9).
Prior to 2.6.28, it is important that mdadm chooses the correct type
of array device to use. This can be controlled with the
.B auto=
on the ARRAY line for the relevant array.
-.SS Auto Assembly
+.SS Auto-Assembly
When
.B \-\-assemble
is used with
.IR mdadm.conf (5)
for further details.
-Note: Auto assembly cannot be used for assembling and activating some
+Note: Auto-assembly cannot be used for assembling and activating some
arrays which are undergoing reshape. In particular as the
.B backup\-file
-cannot be given, any reshape which requires a backup-file to continue
-cannot be started by auto assembly. An array which is growing to more
+cannot be given, any reshape which requires a backup file to continue
+cannot be started by auto-assembly. An array which is growing to more
devices and has passed the critical section can be assembled using
auto-assembly.
.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
+(non fs-data). This type of 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.
setting.
.\"If the
.\".B \-\-size
-.\"option is given, it is not necessary to list any component-devices in this command.
+.\"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 \-\-bitmap
option or a different consistency policy is selected with the
.B \-\-consistency\-policy
-option. In any case space for a bitmap will be reserved so that one
+option. In any case, space for a bitmap will be reserved so that one
can be added later with
.BR "\-\-grow \-\-bitmap=internal" .
as faulty in
.B /dev/md0
and will then remove it from the array and finally add it back
-in as a spare. However only one md array can be affected by a single
+in as a spare. However, only one md array can be affected by a single
command.
When a device is added to an active array, mdadm checks to see if it
If the device contains RAID metadata, a file will be created in the
.I directory
and the metadata will be written to it. The file will be the same
-size as the device and have the metadata written in the file at the
-same locate that it exists in the device. However the file will be "sparse" so
+size as the device and will have the metadata written at the
+same location as it exists in the device. However, the file will be "sparse" so
that only those blocks containing metadata will be allocated. The
total space used will be small.
-The file name used in the
+The filename used in the
.I directory
-will be the base name of the device. Further if any links appear in
+will be the base name of the device. Further, if any links appear in
.I /dev/disk/by-id
which point to the device, then hard links to the file will be created
in
If any devices are listed on the command line,
.I mdadm
-will only monitor those devices. Otherwise all arrays listed in the
+will only monitor those devices, otherwise, all arrays listed in the
configuration file will be monitored. Further, if
.B \-\-scan
is given, then any other md devices that appear in
.BI Rebuild NN
Where
.I NN
-is a two-digit number (ie. 05, 48). This indicates that rebuild
-has passed that many percent of the total. The events are generated
-with fixed increment since 0. Increment size may be specified with
-a commandline option (default is 20). (syslog priority: Warning)
+is a two-digit number (eg. 05, 48). This indicates that the rebuild
+has reached that percentage of the total. The events are generated
+at a fixed increment from 0. The increment size may be specified with
+a command-line option (the default is 20). (syslog priority: Warning)
.TP
.B RebuildFinished
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
-attempt to remove the spare from the second drive and add it to the
+has a full complement of working drives and a spare. It will then
+attempt to remove the spare from the second array and add it to the
first.
If the removal succeeds but the adding fails, then it is added back to
the original array.
.SH GROW MODE
The GROW mode is used for changing the size or shape of an active
array.
-For this to work, the kernel must support the necessary change.
-Various types of growth are being added during 2.6 development.
-Currently the supported changes include
+During the kernel 2.6 era the following changes were added:
.IP \(bu 4
change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
.IP \(bu 4
.SS SIZE CHANGES
Normally when an array is built the "size" is 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
+of the drives. If all the small drives in an arrays are, over time,
+removed and replaced with larger drives, then you could have an
array of large drives with only a small amount used. In this
situation, changing the "size" with "GROW" mode will allow the extra
space to start being used. If the size is increased in this way, a
.B prior
to shrinking the array.
-Also the size of an array cannot be changed while it has an active
+Also, the size of an array cannot be changed while it has an active
bitmap. If an array has a bitmap, it must be removed before the size
can be changed. Once the change is complete a new bitmap can be created.
is required. If the array is not simultaneously being grown or
shrunk, so that the array size will remain the same - for example,
reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
-be used not just for a "cricital section" but throughout the reshape
+be used not just for a "critical section" but throughout the reshape
operation, as described below under LAYOUT CHANGES.
.SS CHUNK-SIZE AND LAYOUT CHANGES
If the reshape is interrupted for any reason, this backup file must be
made available to
.B "mdadm --assemble"
-so the array can be reassembled. Consequently the file cannot be
+so the array can be reassembled. Consequently, the file cannot be
stored on the device being reshaped.
projects / thirdparty / mdadm.git / commitdiff
