"Fossies" - the Fresh Open Source Software Archive  

Source code changes of the file "mdadm.8.in" between
mdadm-4.1.tar.gz and mdadm-4.2.tar.gz

About: mdadm is a tool for creating, managing and monitoring device arrays using the "md" driver in Linux, also known as Software RAID arrays.

mdadm.8.in  (mdadm-4.1)	:	mdadm.8.in  (mdadm-4.2)
.\" -*- nroff -*-		.\" -*- nroff -*-
.\" Copyright Neil Brown and others.		.\" Copyright Neil Brown and others.
.\" This program is free software; you can redistribute it and/or modify		.\" 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		.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or		.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.		.\" (at your option) any later version.
.\" See file COPYING in distribution for details.		.\" See file COPYING in distribution for details.
.TH MDADM 8 "" v4.1-rc2		.TH MDADM 8 "" v4.2
.SH NAME		.SH NAME
mdadm \- manage MD devices		mdadm \- manage MD devices
.I aka		.I aka
Linux Software RAID		Linux Software RAID
.SH SYNOPSIS		.SH SYNOPSIS
.BI mdadm " [mode] <raiddevice> [options] <component-devices>"		.BI mdadm " [mode] <raiddevice> [options] <component-devices>"
.SH DESCRIPTION		.SH DESCRIPTION
skipping to change at line 369		skipping to change at line 369
SNIA.		SNIA.
When creating a DDF array a		When creating a DDF array a
.B CONTAINER		.B CONTAINER
will be created, and normal arrays can be created in that container.		will be created, and normal arrays can be created in that container.
.IP imsm		.IP imsm
Use the Intel(R) Matrix Storage Manager metadata format. This creates a		Use the Intel(R) Matrix Storage Manager metadata format. This creates a
.B CONTAINER		.B CONTAINER
which is managed in a similar manner to DDF, and is supported by an		which is managed in a similar manner to DDF, and is supported by an
option-rom on some platforms:		option-rom on some platforms:
.IP		.IP
.B http://www.intel.com/design/chipsets/matrixstorage_sb.htm		.B https://www.intel.com/content/www/us/en/support/products/122484/memory-and-st orage/ssd-software/intel-virtual-raid-on-cpu-intel-vroc.html
.PP		.PP
.RE		.RE
.TP		.TP
.B \-\-homehost=		.B \-\-homehost=
This will override any		This will override any
.B HOMEHOST		.B HOMEHOST
setting in the config file and provides the identity 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.		should be considered the home for any arrays.
skipping to change at line 469		skipping to change at line 469
.TP		.TP
.BR \-z ", " \-\-size=		.BR \-z ", " \-\-size=
Amount (in Kilobytes) of space to use from each drive in RAID levels 1/4/5/6.		Amount (in Kilobytes) of space to use from each drive in RAID levels 1/4/5/6.
This must be a multiple of the chunk size, and must leave about 128Kb		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.		of space at the end of the drive for the RAID superblock.
If this is not specified		If this is not specified
(as it normally is not) the smallest drive (or partition) sets the		(as it normally is not) the smallest drive (or partition) sets the
size, though if there is a variance among the drives of greater than 1%, a warni ng is		size, though if there is a variance among the drives of greater than 1%, a warni ng is
issued.		issued.
A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or		A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
Gigabytes respectively.		Megabytes, Gigabytes or Terabytes respectively.
Sometimes a replacement drive can be a little smaller than the		Sometimes a replacement drive can be a little smaller than the
original drives though this should be minimised by IDEMA standards.		original drives though this should be minimised by IDEMA standards.
Such a replacement drive will be rejected by		Such a replacement drive will be rejected by
.IR md .		.IR md .
To guard against this it can be useful to set the initial size		To guard against this it can be useful to set the initial size
slightly smaller than the smaller device with the aim that it will		slightly smaller than the smaller device with the aim that it will
still be larger than any replacement.		still be larger than any replacement.
This value can be set with		This value can be set with
.B \-\-grow		.B \-\-grow
for RAID level 1/4/5/6 though		for RAID level 1/4/5/6 though
.B CONTAINER		DDF arrays may not be able to support this.
based arrays such as those with IMSM metadata may not be able to
support this.
If the array was created with a size smaller than the currently		If the array was created with a size smaller than the currently
active drives, the extra space can be accessed using		active drives, the extra space can be accessed using
.BR \-\-grow .		.BR \-\-grow .
The size can be given as		The size can be given as
.B max		.B max
which means to choose the largest size that fits on all current drives.		which means to choose the largest size that fits on all current drives.
Before reducing the size of the array (with		Before reducing the size of the array (with
.BR "\-\-grow \-\-size=" )		.BR "\-\-grow \-\-size=" )
you should make sure that space isn't needed. If the device holds a		you should make sure that space isn't needed. If the device holds a
skipping to change at line 536		skipping to change at line 534
isn't needed. If the device holds a filesystem, you would need to		isn't needed. If the device holds a filesystem, you would need to
resize the filesystem to use less space.		resize the filesystem to use less space.
After reducing the array size you should check that the data stored in		After reducing the array size you should check that the data stored in
the device is still available. If the device holds a filesystem, then		the device is still available. If the device holds a filesystem, then
an 'fsck' of the filesystem is a minimum requirement. If there are		an 'fsck' of the filesystem is a minimum requirement. If there are
problems the array can be made bigger again with no loss with another		problems the array can be made bigger again with no loss with another
.B "\-\-grow \-\-array\-size="		.B "\-\-grow \-\-array\-size="
command.		command.
A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or		A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
Gigabytes respectively.		Megabytes, Gigabytes or Terabytes respectively.
A value of		A value of
.B max		.B max
restores the apparent size of the array to be whatever the real		restores the apparent size of the array to be whatever the real
amount of available space is.		amount of available space is.
Clustered arrays do not support this parameter yet.		Clustered arrays do not support this parameter yet.
.TP		.TP
.BR \-c ", " \-\-chunk=		.BR \-c ", " \-\-chunk=
Specify chunk size of kilobytes. The default when creating an		Specify chunk size of kilobytes. The default when creating an
array is 512KB. To ensure compatibility with earlier versions, the		array is 512KB. To ensure compatibility with earlier versions, the
default when building an array with no persistent metadata is 64KB.		default when building an array with no persistent metadata is 64KB.
This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.		This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power		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. In any case it must be a multiple of 4KB.
A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or		A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
Gigabytes respectively.		Megabytes, Gigabytes or Terabytes respectively.
.TP		.TP
.BR \-\-rounding=		.BR \-\-rounding=
Specify rounding factor for a Linear array. The size of each		Specify rounding factor for a Linear array. The size of each
component will be rounded down to a multiple of this size.		component will be rounded down to a multiple of this size.
This is a synonym for		This is a synonym for
.B \-\-chunk		.B \-\-chunk
but highlights the different meaning for Linear as compared to other		but highlights the different meaning for Linear as compared to other
RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in		RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
use, and is 0K (i.e. no rounding) in later kernels.		use, and is 0K (i.e. no rounding) in later kernels.
skipping to change at line 595		skipping to change at line 593
Can be used with		Can be used with
.B \-\-grow		.B \-\-grow
to change the RAID level in some cases. See LEVEL CHANGES below.		to change the RAID level in some cases. See LEVEL CHANGES below.
.TP		.TP
.BR \-p ", " \-\-layout=		.BR \-p ", " \-\-layout=
This option configures the fine details of data layout for RAID5, RAID6,		This option configures the fine details of data layout for RAID5, RAID6,
and RAID10 arrays, and controls the failure modes for		and RAID10 arrays, and controls the failure modes for
.IR faulty .		.IR faulty .
		It can also be used for working around a kernel bug with RAID0, but generally
		doesn't need to be used explicitly.
The layout of the RAID5 parity block can be one of		The layout of the RAID5 parity block can be one of
.BR left\-asymmetric ,		.BR left\-asymmetric ,
.BR left\-symmetric ,		.BR left\-symmetric ,
.BR right\-asymmetric ,		.BR right\-asymmetric ,
.BR right\-symmetric ,		.BR right\-symmetric ,
.BR la ", " ra ", " ls ", " rs .		.BR la ", " ra ", " ls ", " rs .
The default is		The default is
.BR left\-symmetric .		.BR left\-symmetric .
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generated after that many requests, and will continue to be generated		generated after that many requests, and will continue to be generated
every time the period elapses.		every time the period elapses.
Multiple failure modes can be current simultaneously by using the		Multiple failure modes can be current simultaneously by using the
.B \-\-grow		.B \-\-grow
option to set subsequent failure modes.		option to set subsequent failure modes.
"clear" or "none" will remove any pending or periodic failure modes,		"clear" or "none" will remove any pending or periodic failure modes,
and "flush" will clear any persistent faults.		and "flush" will clear any persistent faults.
Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed		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. The default is 'n2'. The supported options are:
.I 'n'		.I 'n'
signals 'near' copies. Multiple copies of one data block are at		signals 'near' copies. Multiple copies of one data block are at
similar offsets in different devices.		similar offsets in different devices.
.I 'o'		.I 'o'
signals 'offset' copies. Rather than the chunks being duplicated		signals 'offset' copies. Rather than the chunks being duplicated
within a stripe, whole stripes are duplicated but are rotated by one		within a stripe, whole stripes are duplicated but are rotated by one
device so duplicate blocks are on different devices. Thus subsequent		device so duplicate blocks are on different devices. Thus subsequent
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signals 'far' copies		signals 'far' copies
(multiple copies have very different offsets).		(multiple copies have very different offsets).
See md(4) for more detail about 'near', 'offset', and 'far'.		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		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		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		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		number (e.g. it is perfectly legal to have an 'n2' layout for an array
with an odd number of devices).		with an odd number of devices).
		A bug introduced in Linux 3.14 means that RAID0 arrays
		.B "with devices of differing sizes"
		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
		.RB ' original '
		or
		.RB ' alternate '.
		When creating a new array,
		.I mdadm
		will select
		.RB ' original '
		by default, so the layout does not normally need to be set.
		An array created for either
		.RB ' original '
		or
		.RB ' alternate '
		will not be recognized by an (unpatched) kernel prior to 5.4. To create
		a RAID0 array with devices of differing sizes that can be used on an
		older kernel, you can set the layout to
		.RB ' dangerous '.
		This will use whichever layout the running kernel supports, so the data
		on the array may become corrupt when changing kernel from pre-3.14 to a
		later kernel.
When an array is converted between RAID5 and RAID6 an intermediate		When an array is converted between RAID5 and RAID6 an intermediate
RAID6 layout is used in which the second parity block (Q) is always on		RAID6 layout is used in which the second parity block (Q) is always on
the last device. To convert a RAID5 to RAID6 and leave it in this new		the last device. To convert a RAID5 to RAID6 and leave it in this new
layout (which does not require re-striping) use		layout (which does not require re-striping) use
.BR \-\-layout=preserve .		.BR \-\-layout=preserve .
This will try to avoid any restriping.		This will try to avoid any restriping.
The converse of this is		The converse of this is
.B \-\-layout=normalise		.B \-\-layout=normalise
which will change a non-standard RAID6 layout into a more standard		which will change a non-standard RAID6 layout into a more standard
skipping to change at line 743		skipping to change at line 769
.BR \-\-bitmap\-chunk=		.BR \-\-bitmap\-chunk=
Set the chunksize of the bitmap. Each bit corresponds to that many		Set the chunksize of the bitmap. Each bit corresponds to that many
Kilobytes of storage.		Kilobytes of storage.
When using a file based bitmap, the default is to use the smallest		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.		size that is at-least 4 and requires no more than 2^21 chunks.
When using an		When using an
.B internal		.B internal
bitmap, the chunksize defaults to 64Meg, or larger if necessary to		bitmap, the chunksize defaults to 64Meg, or larger if necessary to
fit the bitmap into the available space.		fit the bitmap into the available space.
A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or		A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
Gigabytes respectively.		Megabytes, Gigabytes or Terabytes respectively.
.TP		.TP
.BR \-W ", " \-\-write\-mostly		.BR \-W ", " \-\-write\-mostly
subsequent devices listed in a		subsequent devices listed in a
.BR \-\-build ,		.BR \-\-build ,
.BR \-\-create ,		.BR \-\-create ,
or		or
.B \-\-add		.B \-\-add
command will be flagged as 'write\-mostly'. This is valid for RAID1		command will be flagged as 'write\-mostly'. This is valid for RAID1
only and means that the 'md' driver will avoid reading from these		only and means that the 'md' driver will avoid reading from these
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device and the start of array data. This gap can be used for various		device and the start of array data. This gap can be used for various
metadata. The start of data is known as the		metadata. The start of data is known as the
.IR data\-offset .		.IR data\-offset .
Normally an appropriate data offset is computed automatically.		Normally an appropriate data offset is computed automatically.
However it can be useful to set it explicitly such as when re-creating		However it can be useful to set it explicitly such as when re-creating
an array which was originally created using a different version of		an array which was originally created using a different version of
.I mdadm		.I mdadm
which computed a different offset.		which computed a different offset.
Setting the offset explicitly over-rides the default. The value given		Setting the offset explicitly over-rides the default. The value given
is in Kilobytes unless a suffix of 'K', 'M' or 'G' is used to explicitly		is in Kilobytes unless a suffix of 'K', 'M', 'G' or 'T' is used to explicitly
indicate Kilobytes, Megabytes or Gigabytes respectively.		indicate Kilobytes, Megabytes, Gigabytes or Terabytes respectively.
Since Linux 3.4,		Since Linux 3.4,
.B \-\-data\-offset		.B \-\-data\-offset
can also be used with		can also be used with
.B --grow		.B --grow
for some RAID levels (initially on RAID10). This allows the		for some RAID levels (initially on RAID10). This allows the
data\-offset to be changed as part of the reshape process. When the		data\-offset to be changed as part of the reshape process. When the
data offset is changed, no backup file is required as the difference		data offset is changed, no backup file is required as the difference
in offsets is used to provide the same functionality.		in offsets is used to provide the same functionality.
skipping to change at line 1107		skipping to change at line 1133
.I homehost		.I homehost
prefixed to the start of the given name.		prefixed to the start of the given name.
.TP		.TP
.BR \-f ", " \-\-force		.BR \-f ", " \-\-force
Assemble the array even if the metadata on some devices appears to be		Assemble the array even if the metadata on some devices appears to be
out-of-date. If		out-of-date. If
.I mdadm		.I mdadm
cannot find enough working devices to start the array, but can find		cannot find enough working devices to start the array, but can find
some devices that are recorded as having failed, then it will mark		some devices that are recorded as having failed, then it will mark
those devices as working so that the array can be started.		those devices as working so that the array can be started. This works only for
		native. For external metadata it allows to start dirty degraded RAID 4, 5, 6.
An array which requires		An array which requires
.B \-\-force		.B \-\-force
to be started may contain data corruption. Use it carefully.		to be started may contain data corruption. Use it carefully.
.TP		.TP
.BR \-R ", " \-\-run		.BR \-R ", " \-\-run
Attempt to start the array even if fewer drives were given than were		Attempt to start the array even if fewer drives were given than were
present last time the array was active. Normally if not all the		present last time the array was active. Normally if not all the
expected drives are found and		expected drives are found and
.B \-\-scan		.B \-\-scan
skipping to change at line 1185		skipping to change at line 1212
.BR homehost ,		.BR homehost ,
.BR home-cluster ,		.BR home-cluster ,
.BR resync ,		.BR resync ,
.BR byteorder ,		.BR byteorder ,
.BR devicesize ,		.BR devicesize ,
.BR no\-bitmap ,		.BR no\-bitmap ,
.BR bbl ,		.BR bbl ,
.BR no\-bbl ,		.BR no\-bbl ,
.BR ppl ,		.BR ppl ,
.BR no\-ppl ,		.BR no\-ppl ,
		.BR layout\-original ,
		.BR layout\-alternate ,
		.BR layout\-unspecified ,
.BR metadata ,		.BR metadata ,
or		or
.BR super\-minor .		.BR super\-minor .
The		The
.B sparc2.2		.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		machine running a patched 2.2 Linux kernel. This kernel got the
alignment of part of the superblock wrong. You can use the		alignment of part of the superblock wrong. You can use the
.B "\-\-examine \-\-sparc2.2"		.B "\-\-examine \-\-sparc2.2"
skipping to change at line 1336		skipping to change at line 1366
The		The
.B ppl		.B ppl
option will enable PPL for a RAID5 array and reserve space for PPL on each		option will enable PPL for a RAID5 array and reserve space for PPL on each
device. There must be enough free space between the data and superblock and a		device. There must be enough free space between the data and superblock and a
write-intent bitmap or journal must not be used.		write-intent bitmap or journal must not be used.
The		The
.B no\-ppl		.B no\-ppl
option will disable PPL in the superblock.		option will disable PPL in the superblock.
		The
		.B layout\-original
		and
		.B layout\-alternate
		options are for RAID0 arrays with non-uniform devices size that were in
		use before Linux 5.4. If the array was being used with Linux 3.13 or
		earlier, then to assemble the array on a new kernel,
		.B \-\-update=layout\-original
		must be given. If the array was created and used with a kernel from Linux 3.14
		to
		Linux 5.3, then
		.B \-\-update=layout\-alternate
		must be given. This only needs to be given once. Subsequent assembly of the ar
		ray
		will happen normally.
		For more information, see
		.IR md (4).
		The
		.B layout\-unspecified
		option reverts the effect of
		.B layout\-orignal
		or
		.B layout\-alternate
		and allows the array to be again used on a kernel prior to Linux 5.3.
		This option should be used with great caution.
.TP		.TP
.BR \-\-freeze\-reshape		.BR \-\-freeze\-reshape
Option is intended to be used in start-up scripts during initrd boot phase.		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		When array under reshape is assembled during initrd phase, this option
stops reshape after reshape critical section is being restored. This happens		stops reshape after reshape critical section is being restored. This happens
before file system pivot operation and avoids loss of file system context.		before file system pivot operation and avoids loss of file system context.
Losing file system context would cause reshape to be broken.		Losing file system context would cause reshape to be broken.
Reshape can be continued later using the		Reshape can be continued later using the
.B \-\-continue		.B \-\-continue
skipping to change at line 1652		skipping to change at line 1707
Report information about a bitmap file.		Report information about a bitmap file.
The argument is either an external bitmap file or an array component		The argument is either an external bitmap file or an array component
in case of an internal bitmap. Note that running this on an array		in case of an internal bitmap. Note that running this on an array
device (e.g.		device (e.g.
.BR /dev/md0 )		.BR /dev/md0 )
does not report the bitmap for that array.		does not report the bitmap for that array.
.TP		.TP
.B \-\-examine\-badblocks		.B \-\-examine\-badblocks
List the bad-blocks recorded for the device, if a bad-blocks list has		List the bad-blocks recorded for the device, if a bad-blocks list has
been configured. Currently only		been configured. Currently only
.B 1.x		.B 1.x
metadata supports bad-blocks lists.		and
		.B IMSM
		metadata support bad-blocks lists.
.TP		.TP
.BI \-\-dump= directory		.BI \-\-dump= directory
.TP		.TP
.BI \-\-restore= directory		.BI \-\-restore= directory
Save metadata from lists devices, or restore metadata to listed devices.		Save metadata from lists devices, or restore metadata to listed devices.
.TP		.TP
.BR \-R ", " \-\-run		.BR \-R ", " \-\-run
start a partially assembled array. If		start a partially assembled array. If
skipping to change at line 2129		skipping to change at line 2186
.PP		.PP
This usage will initialise a new md array, associate some devices with		This usage will initialise a new md array, associate some devices with
it, and activate the array.		it, and activate the array.
The named device will normally not exist when		The named device will normally not exist when
.I "mdadm \-\-create"		.I "mdadm \-\-create"
is run, but will be created by		is run, but will be created by
.I udev		.I udev
once the array becomes active.		once the array becomes active.
		The max length md-device name is limited to 32 characters.
		Different metadata types have more strict limitation
		(like IMSM where only 16 characters are allowed).
		For that reason, long name could be truncated or rejected, it depends on metadat
		a policy.
As devices are added, they are checked to see if they contain RAID		As devices are added, they are checked to see if they contain RAID
superblocks or filesystems. They are also checked to see if the variance in		superblocks or filesystems. They are also checked to see if the variance in
device size exceeds 1%.		device size exceeds 1%.
If any discrepancy is found, the array will not automatically be run, though		If any discrepancy is found, the array will not automatically be run, though
the presence of a		the presence of a
.B \-\-run		.B \-\-run
can override this caution.		can override this caution.
To create a "degraded" array in which some devices are missing, simply		To create a "degraded" array in which some devices are missing, simply
skipping to change at line 2352		skipping to change at line 2414
.B \-\-update\-subarray=		.B \-\-update\-subarray=
If the device is a container and the argument to \-\-update\-subarray		If the device is a container and the argument to \-\-update\-subarray
specifies a subarray in the container, then attempt to update the given		specifies a subarray in the container, then attempt to update the given
superblock field in the subarray. Similar to updating an array in		superblock field in the subarray. Similar to updating an array in
"assemble" mode, the field to update is selected by		"assemble" mode, the field to update is selected by
.B \-U		.B \-U
or		or
.B \-\-update=		.B \-\-update=
option. The supported options are		option. The supported options are
.BR name ,		.BR name ,
.B ppl		.BR ppl ,
		.BR no\-ppl ,
		.BR bitmap
and		and
.BR no\-ppl .		.BR no\-bitmap .
The		The
.B name		.B name
option updates the subarray name in the metadata, it may not affect the		option updates the subarray name in the metadata, it may not affect the
device node name or the device node symlink until the subarray is		device node name or the device node symlink until the subarray is
re\-assembled. If updating		re\-assembled. If updating
.B name		.B name
would change the UUID of an active subarray this operation is blocked,		would change the UUID of an active subarray this operation is blocked,
and the command will end in an error.		and the command will end in an error.
The		The
.B ppl		.B ppl
and		and
.B no\-ppl		.B no\-ppl
options enable and disable PPL in the metadata. Currently supported only for		options enable and disable PPL in the metadata. Currently supported only for
IMSM subarrays.		IMSM subarrays.
		The
		.B bitmap
		and
		.B no\-bitmap
		options enable and disable write-intent bitmap in the metadata. Currently suppor
		ted only for
		IMSM subarrays.
.TP		.TP
.B \-\-examine		.B \-\-examine
The device should be a component of an md array.		The device should be a component of an md array.
.I mdadm		.I mdadm
will read the md superblock of the device and display the contents.		will read the md superblock of the device and display the contents.
If		If
.B \-\-brief		.B \-\-brief
or		or
.B \-\-scan		.B \-\-scan
is given, then multiple devices that are components of the one array		is given, then multiple devices that are components of the one array
skipping to change at line 2714		skipping to change at line 2785
remove a write-intent bitmap from such an array.		remove a write-intent bitmap from such an array.
.IP \(bu 4		.IP \(bu 4
change the array's consistency policy.		change the array's consistency policy.
.PP		.PP
Using GROW on containers is currently supported only for Intel's IMSM		Using GROW on containers is currently supported only for Intel's IMSM
container format. The number of devices in a container can be		container format. The number of devices in a container can be
increased - which affects all arrays in the container - or an array		increased - which affects all arrays in the container - or an array
in a container can be converted between levels where those levels are		in a container can be converted between levels where those levels are
supported by the container, and the conversion is on of those listed		supported by the container, and the conversion is on of those listed
above. Resizing arrays in an IMSM container with		above.
.B "--grow --size"
is not yet supported.
.PP		.PP
Notes:		Notes:
.IP \(bu 4		.IP \(bu 4
Intel's native checkpointing doesn't use		Intel's native checkpointing doesn't use
.B --backup-file		.B --backup-file
option and it is transparent for assembly feature.		option and it is transparent for assembly feature.
.IP \(bu 4		.IP \(bu 4
Roaming between Windows(R) and Linux systems for IMSM metadata is not		Roaming between Windows(R) and Linux systems for IMSM metadata is not
supported during grow process.		supported during grow process.
		.IP \(bu 4
		When growing a raid0 device, the new component disk size (or external
		backup size) should be larger than LCM(old, new) * chunk-size * 2,
		where LCM() is the least common multiple of the old and new count of
		component disks, and "* 2" comes from the fact that mdadm refuses to
		use more than half of a spare device for backup space.
.SS SIZE CHANGES		.SS SIZE CHANGES
Normally when an array is built the "size" is taken from the smallest		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		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		time, removed and replaced with larger drives, then you could have an
array of large drives with only a small amount used. In this		array of large drives with only a small amount used. In this
situation, changing the "size" with "GROW" mode will allow the extra		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		space to start being used. If the size is increased in this way, a
"resync" process will start to make sure the new parts of the array		"resync" process will start to make sure the new parts of the array
are synchronised.		are synchronised.
skipping to change at line 2831		skipping to change at line 2906
long time. A		long time. A
.B \-\-backup\-file		.B \-\-backup\-file
is required. If the array is not simultaneously being grown or		is required. If the array is not simultaneously being grown or
shrunk, so that the array size will remain the same - for example,		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		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 "cricital section" but throughout the reshape
operation, as described below under LAYOUT CHANGES.		operation, as described below under LAYOUT CHANGES.
.SS CHUNK-SIZE AND LAYOUT CHANGES		.SS CHUNK-SIZE AND LAYOUT CHANGES
Changing the chunk-size of layout without also changing the number of		Changing the chunk-size or layout without also changing the number of
devices as the same time will involve re-writing all blocks in-place.		devices as the same time will involve re-writing all blocks in-place.
To ensure against data loss in the case of a crash, a		To ensure against data loss in the case of a crash, a
.B --backup-file		.B --backup-file
must be provided for these changes. Small sections of the array will		must be provided for these changes. Small sections of the array will
be copied to the backup file while they are being rearranged. This		be copied to the backup file while they are being rearranged. This
means that all the data is copied twice, once to the backup and once		means that all the data is copied twice, once to the backup and once
to the new layout on the array, so this type of reshape will go very		to the new layout on the array, so this type of reshape will go very
slowly.		slowly.
If the reshape is interrupted for any reason, this backup file must be		If the reshape is interrupted for any reason, this backup file must be
skipping to change at line 3358		skipping to change at line 3433
.SH NOTE		.SH NOTE
.I mdadm		.I mdadm
was previously known as		was previously known as
.IR mdctl .		.IR mdctl .
.SH SEE ALSO		.SH SEE ALSO
For further information on mdadm usage, MD and the various levels of		For further information on mdadm usage, MD and the various levels of
RAID, see:		RAID, see:
.IP		.IP
.B http://raid.wiki.kernel.org/		.B https://raid.wiki.kernel.org/
.PP		.PP
(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)		(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
.PP		.PP
The latest version of		The latest version of
.I mdadm		.I mdadm
should always be available from		should always be available from
.IP		.IP
.B http://www.kernel.org/pub/linux/utils/raid/mdadm/		.B https://www.kernel.org/pub/linux/utils/raid/mdadm/
.PP		.PP
Related man pages:		Related man pages:
.PP		.PP
.IR mdmon (8),		.IR mdmon (8),
.IR mdadm.conf (5),		.IR mdadm.conf (5),
.IR md (4).		.IR md (4).
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