.\" 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 "" v4.1-rc2
+.TH MDADM 8 "" v4.2
.SH NAME
mdadm \- manage MD devices
.I aka
.TP
.BR \-c ", " \-\-config=
-Specify the config file or directory. Default is to use
-.B /etc/mdadm.conf
-and
-.BR /etc/mdadm.conf.d ,
-or if those are missing then
-.B /etc/mdadm/mdadm.conf
-and
-.BR /etc/mdadm/mdadm.conf.d .
+Specify the config file or directory. If not specified, default config file
+and default conf.d directory will be used. See
+.BR mdadm.conf (5)
+for more details.
+
If the config file given is
.B "partitions"
then nothing will be read, but
which is managed in a similar manner to DDF, and is supported by an
option-rom on some platforms:
.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-storage/ssd-software/intel-virtual-raid-on-cpu-intel-vroc.html
.PP
.RE
.TP
.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 1/4/5/6/10
+and for RAID 0 on external metadata.
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
size, though if there is a variance among the drives of greater than 1%, a warning is
issued.
-A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
-Gigabytes respectively.
+A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
+Megabytes, Gigabytes or Terabytes respectively.
Sometimes a replacement drive can be a little smaller than the
original drives though this should be minimised by IDEMA standards.
slightly smaller than the smaller device with the aim that it will
still be larger than any replacement.
+This option can be used with
+.B \-\-create
+for determining 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
+.B RAID 0
+array is only valid for external metadata.
+
This value can be set with
.B \-\-grow
-for RAID level 1/4/5/6 though
-.B CONTAINER
-based arrays such as those with IMSM metadata may not be able to
-support this.
+for RAID level 1/4/5/6/10 though
+DDF arrays may not be able to support this.
+RAID 0 array size cannot be changed.
If the array was created with a size smaller than the currently
active drives, the extra space can be accessed using
.BR \-\-grow .
.B "\-\-grow \-\-size="
command.
-This value cannot be used when creating a
-.B CONTAINER
-such as with DDF and IMSM metadata, though it perfectly valid when
-creating an array inside a container.
-
.TP
.BR \-Z ", " \-\-array\-size=
This is only meaningful with
.B "\-\-grow \-\-array\-size="
command.
-A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
-Gigabytes respectively.
+A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
+Megabytes, Gigabytes or Terabytes respectively.
A value of
.B max
restores the apparent size of the array to be whatever the real
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.
-A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
-Gigabytes respectively.
+A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
+Megabytes, Gigabytes or Terabytes respectively.
.TP
.BR \-\-rounding=
bitmap, the chunksize defaults to 64Meg, or larger if necessary to
fit the bitmap into the available space.
-A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
-Gigabytes respectively.
+A suffix of 'K', 'M', 'G' or 'T' can be given to indicate Kilobytes,
+Megabytes, Gigabytes or Terabytes respectively.
.TP
.BR \-W ", " \-\-write\-mostly
which computed a different offset.
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
-indicate Kilobytes, Megabytes or Gigabytes respectively.
+is in Kilobytes unless a suffix of 'K', 'M', 'G' or 'T' is used to explicitly
+indicate Kilobytes, Megabytes, Gigabytes or Terabytes respectively.
Since Linux 3.4,
.B \-\-data\-offset
Specify journal device for the RAID-4/5/6 array. The journal device
should be a SSD with reasonable lifetime.
-.TP
-.BR \-\-symlinks
-Auto creation of symlinks in /dev to /dev/md, option --symlinks must
-be 'no' or 'yes' and work with --create and --build.
-
.TP
.BR \-k ", " \-\-consistency\-policy=
Specify how the array maintains consistency in case of unexpected shutdown.
.I mdadm
cannot find enough working devices to start the array, but can find
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
.B \-\-force
to be started may contain data corruption. Use it carefully.
.BR no\-bbl ,
.BR ppl ,
.BR no\-ppl ,
+.BR layout\-original ,
+.BR layout\-alternate ,
+.BR layout\-unspecified ,
.BR metadata ,
or
.BR super\-minor .
.B no\-ppl
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 array
+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
.BR \-\-freeze\-reshape
Option is intended to be used in start-up scripts during initrd boot phase.
.B \-\-continue
option for the grow command.
-.TP
-.BR \-\-symlinks
-See this option under Create and Build options.
-
.SH For Manage mode:
.TP
.TP
.B \-\-examine\-badblocks
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
-metadata supports bad-blocks lists.
+and
+.B IMSM
+metadata support bad-blocks lists.
.TP
.BI \-\-dump= directory
.B \-\-config
or requested with (a possibly implicit)
.BR \-\-scan .
-In the later case,
-.B /etc/mdadm.conf
-or
-.B /etc/mdadm/mdadm.conf
-is used.
+In the later case, default config file is used. See
+.BR mdadm.conf (5)
+for more details.
If
.B \-\-scan
.I udev
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 metadata policy.
+
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
device size exceeds 1%.
.B \-\-update=
option. The supported options are
.BR name ,
-.B ppl
+.BR ppl ,
+.BR no\-ppl ,
+.BR bitmap
and
-.BR no\-ppl .
+.BR no\-bitmap .
The
.B name
options enable and disable PPL in the metadata. Currently supported only for
IMSM subarrays.
+The
+.B bitmap
+and
+.B no\-bitmap
+options enable and disable write-intent bitmap in the metadata. Currently supported only for
+IMSM subarrays.
+
.TP
.B \-\-examine
The device should be a component of an md array.
increased - which affects all arrays in the container - or an array
in a container can be converted between levels where those levels are
supported by the container, and the conversion is on of those listed
-above. Resizing arrays in an IMSM container with
-.B "--grow --size"
-is not yet supported.
+above.
.PP
Notes:
.IP \(bu 4
Roaming between Windows(R) and Linux systems for IMSM metadata is not
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
Normally when an array is built the "size" is taken from the smallest
.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.
To ensure against data loss in the case of a crash, a
.B --backup-file
is given in Misc mode, and to monitor array reconstruction
on Monitor mode.
-.SS /etc/mdadm.conf
+.SS {CONFFILE} (or {CONFFILE2})
-The config file lists which devices may be scanned to see if
-they contain MD super block, and gives identifying information
-(e.g. UUID) about known MD arrays. See
+Default config file. See
.BR mdadm.conf (5)
for more details.
-.SS /etc/mdadm.conf.d
+.SS {CONFFILE}.d (or {CONFFILE2}.d)
-A directory containing configuration files which are read in lexical
-order.
+Default directory containing configuration files. See
+.BR mdadm.conf (5)
+for more details.
.SS {MAP_PATH}
When
For further information on mdadm usage, MD and the various levels of
RAID, see:
.IP
-.B http://raid.wiki.kernel.org/
+.B https://raid.wiki.kernel.org/
.PP
(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
.PP
.I mdadm
should always be available from
.IP
-.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
+.B https://www.kernel.org/pub/linux/utils/raid/mdadm/
.PP
Related man pages:
.PP
projects / thirdparty / mdadm.git / blobdiff