.\" 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 "" v3.2
+.TH MDADM 8 "" v3.2.2
.SH NAME
mdadm \- manage MD devices
.I aka
A suffix of 'M' or 'G' can be given to indicate Megabytes or
Gigabytes respectively.
+Sometimes a replacement drive can be a little smaller than the
+original drives though this should be minimised by IDEMA standards.
+Such a replacement drive will be rejected by
+.IR md .
+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
+still be larger than any replacement.
+
This value can be set with
.B \-\-grow
-for RAID level 1/4/5/6. If the array was created with a size smaller
-than the currently active drives, the extra space can be accessed
-using
+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.
+If the array was created with a size smaller than the currently
+active drives, the extra space can be accessed using
.BR \-\-grow .
The size can be given as
.B max
.B "\-\-grow \-\-size="
command.
-This value can not be used with
+This value cannot be used when creating a
.B CONTAINER
-metadata such as DDF and IMSM.
+such as with DDF and IMSM metadata, though it perfectly valid when
+creating an array inside a container.
.TP
.BR \-Z ", " \-\-array\-size=
default when Building and 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.
+
A suffix of 'M' or 'G' can be given to indicate Megabytes or
Gigabytes respectively.
actually clean. If that is the case, such as after running
badblocks, this argument can be used to tell mdadm the
facts the operator knows.
+.IP
+When an array is resized to a larger size with
+.B "\-\-grow \-\-size="
+the new space is normally resynced in that same way that the whole
+array is resynced at creation. From Linux version 3.0,
+.B \-\-assume\-clean
+can be used with that command to avoid the automatic resync.
.TP
.BR \-\-backup\-file=
non-standard name. Names that are not in 'standard' format are only
allowed in "/dev/md/".
+This is meaningful with
+.B \-\-create
+or
+.BR \-\-build .
+
.ig XX
.\".TP
.\".BR \-\-symlink = no
.\"
.XX
+.TP
+.BR \-a ", " "\-\-add"
+This option can be used in Grow mode in two cases.
+
+If the target array is a Linear array, then
+.B \-\-add
+can be used to add one or more devices to the array. They
+are simply catenated on to the end of the array. Once added, the
+devices cannot be removed.
+
+If the
+.B \-\-raid\-disks
+option is being used to increase the number of devices in an array,
+then
+.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
+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.
+
.SH For assemble:
.TP
.BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
See this option under Create and Build options.
-.TP
-.BR \-a ", " "\-\-add"
-This option can be used in Grow mode in two cases.
-
-If the target array is a Linear array, then
-.B \-\-add
-can be used to add one or more devices to the array. They
-are simply catenated on to the end of the array. Once added, the
-devices cannot be removed.
-
-If the
-.B \-\-raid\-disks
-option is being used to increase the number of devices in an array,
-then
-.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
-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 \-b ", " \-\-bitmap=
Specify the bitmap file that was given when the array was created. If
corrupt in some way so that assembling the array normally fails. It
will cause any internal bitmap to be ignored.
-.ig
-.TP
-.B \-\-auto\-update\-homehost
-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 rescan for any arrays at all and will assemble them and update the
-homehost to match the current host.
-..
-
.SH For Manage mode:
.TP
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. If not arrays are
+listed in the configuration file are assembled. If no arrays are
described by the configuration file, then any arrays that
can be found on unused devices will be assembled.
will first attempt to assemble all the arrays listed in the config
file.
-In no array at listed in the config (other than those marked
+If no arrays are listed in the config (other than those marked
.BR <ignore> )
it will look through the available devices for possible arrays and
will try to assemble anything that it finds. Arrays which are tagged
.IR mdadm.conf (5)
for further details.
-.ig
-If
-.I mdadm
-cannot find any array for the given host at all, and if
-.B \-\-auto\-update\-homehost
-is given, then
-.I mdadm
-will search again for any array (not just an array created for this
-host) and will assemble each assuming
-.BR \-\-update=homehost .
-This will change the host tag in the superblock so that on the next run,
-these arrays will be found without the second pass. The intention of
-this feature is to support transitioning a set of md arrays to using
-homehost tagging.
-
-The reason for requiring arrays to be tagged with the homehost for
-auto assembly is to guard against problems that can arise when moving
-devices from one host to another.
-..
Note: Auto assembly cannot be used for assembling and activating some
arrays which are undergoing reshape. In particular as the
.B backup\-file
.IP \(bu 4
increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
RAID5, and RAID6.
-.IP \bu 4
+.IP \(bu 4
change the chunk-size and layout of RAID0, RAID4, RAID5 and RAID6.
-.IP \bu 4
+.IP \(bu 4
convert between RAID1 and RAID5, between RAID5 and RAID6, between
-RAID0, RAID5, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
+RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
.IP \(bu 4
add a write-intent bitmap to any array which supports these bitmaps, or
remove a write-intent bitmap from such an array.
.PP
-Using GROW on containers is currently only support 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
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.
+above. Resizing arrays in an IMSM container with
+.B "--grow --size"
+is not yet supported.
Grow functionality (e.g. expand a number of raid devices) for Intel's
IMSM container format has an experimental status. It is guarded by the
This is for the following reasons:
.IP 1.
-Intel's native IMSM check-pointing is not fully implemented yet.
-This causes IMSM incompatibility during the grow process: an array
+Intel's native IMSM check-pointing is not fully tested yet.
+This can causes IMSM incompatibility during the grow process: an array
which is growing cannot roam between Microsoft Windows(R) and Linux
systems.
Interrupting a grow operation is not recommended, because it
has not been fully tested for Intel's IMSM container format yet.
+.PP
+Note: Intel's native checkpointing doesn't use
+.B --backup-file
+option and it is transparent for assembly feature.
+
.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
are synchronised.
Note that when an array changes size, any filesystem that may be
-stored in the array will not automatically grow for shrink to use or
+stored in the array will not automatically grow or shrink to use or
vacate the space. The
filesystem will need to be explicitly told to use the extra space
after growing, or to reduce its size
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 it complete a new bitmap can be created.
+can be changed. Once the change is complete a new bitmap can be created.
.SS RAID\-DEVICES CHANGES
line.
.IP +
-Does the device have a valid md superblock. If a specific metadata
-version is request with
+Does the device have a valid md superblock? If a specific metadata
+version is requested with
.B \-\-metadata
or
.B \-e
current host, the device will be rejected.
..
+.PP
.I mdadm
keeps a list of arrays that it has partially assembled in
.B /var/run/mdadm/map
Any devices which are components of /dev/md4 will be marked as faulty
and then remove from the array.
-.B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4
+.B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
.br
The array
.B /dev/md4
For further information on mdadm usage, MD and the various levels of
RAID, see:
.IP
-.B http://linux\-raid.osdl.org/
+.B http://raid.wiki.kernel.org/
.PP
(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
.\".PP
projects / thirdparty / mdadm.git / blobdiff