.\" -*- nroff -*-
-.TH MDADM 8 "" v2.0-devel-1
+.TH MDADM 8 "" v2.0-devel-3
.SH NAME
mdadm \- manage MD devices
.I aka
.BR RAID4 ,
.BR RAID5 ,
.BR RAID6 ,
+.BR RAID10 ,
.BR MULTIPATH ,
and
.BR FAULTY .
-.B MULTIPATH is not a Software RAID mechanism, but does involve
+.B MULTIPATH
+is not a Software RAID mechanism, but does involve
multiple devices. For
.B MULTIPATH
each device is a path to one common physical storage device.
-.B FAULTY is also no true RAID, and it only involves one device. It
+.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 an different purpose.
+'''.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 an different purpose.
.SH MODES
mdadm has 7 major modes of operation:
.TP
.B Build
-Build an array without per-device superblocks.
+Build an array that doesn't have per-device superblocks. For these
+sorts of arrays,
+.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
+.B Build
+mode should only be used together with a complete understanding of
+what you are doing.
.TP
.B Create
.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 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.
.TP
.BR -h ", " --help
-Display help message or, after above option, mode specific help
-message.
+Display general help message or, after one of the above options, a
+mode specific help message.
.TP
.B --help-options
.BR -v ", " --verbose
Be more verbose about what is happening. This can be used twice to be
extra-verbose.
-This currently only affects
+The extra verbosity currently only affects
.B --detail --scan
and
.BR "--examine --scan" .
+.TP
+.BR -q ", " --quiet
+Avoid printing purely informative messages. With this,
+.B mdadm
+will be silent unless there is something really important to report.
+
.TP
.BR -b ", " --brief
Be less verbose. This is used with
.B --verbose
gives an intermediate level of verbosity.
+.TP
+.BR -W ", " --write-mostly
+subsequent devices lists in a
+.BR --build ,
+.BR --create ,
+or
+.B --add
+command will be flagged as 'write-mostly'. This is valid for RAID1
+only and means that the 'md' driver will avoid reading from these
+devices if at all possible. This can be useful if mirroring over a
+slow link.
+
.TP
.BR -b ", " --bitmap=
Give the name of a bitmap file to use with this array. Can be used
-with --create (file should not exist) or --assemble (file should
-exist).
+with --create (file should not exist), --assemble (file should
+exist), of --grow (file should not exist).
+
+The file
+.B internal
+can be used to indicate that the bitmap should be stored in the array,
+near the superblock. There is a limited amount of space for such
+bitmaps, but it is often sufficient.
+
+The file
+.B none
+can be given when used with --grow to remove a bitmap.
.TP
.BR --bitmap-chunk=
Set the Chunksize of the bitmap. Each bit corresponds to that many
Kilobytes of storage. Default is 4.
+.TP
+.BR --write-behind=
+Specify that write-behind mode should be enabled (valid for RAID1
+only). If an argument is specified, it will set the maximum number
+of outstanding writes allowed. The default value is 256.
+A write-intent bitmap is required in order to use write-behind
+mode, and write-behind is only attempted on drives marked as
+.IR write-mostly .
+
.TP
.BR -f ", " --force
Set raid level. When used with
.IR --create ,
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
-raid5, 5, raid6, 6, multipath, mp, fautly. Obviously some of these are synonymous.
+raid5, 5, raid6, 6, raid10, 10, multipath, mp, fautly. Obviously some of these are synonymous.
When used with
.IR --build ,
-only linear, raid0, 0, stripe are valid.
+only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
.TP
-.BR -p ", " --parity=
-Set raid5 parity algorithm. Options are:
+.BR -p ", " --layout=
+This option configures the fine details of data layout for raid5,
+and raid10 arrays, and controls the failure modes for
+.IR faulty .
+
+The layout of the raid5 parity block can be one of
left-asymmetric,
left-symmetric,
right-asymmetric,
right-symmetric,
la, ra, ls, rs. The default is left-symmetric.
-This option is also used to set the failure mode for
-.IR faulty .
-The options are:
+When setting the failure mode for
+.I faulty
+the options are:
write-transient,
wt,
read-transient,
To set the parity with "--grow", the level of the array ("faulty")
must be specified before the fault mode is specified.
+Finally, the layout options for RAID10 are either 'n' or 'p' followed
+by a small number. The default is 'n2'.
+
+.I n
+signals 'near' copies (multiple copies of one data block are at
+similar offsets in different devices) while
+.I f
+signals 'far' copies
+(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
+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
+with an odd number of devices).
+
.TP
-.BR --layout=
-same as --parity
+.BR --parity=
+same as --layout (thus explaining the p of
+.IR -p ).
.TP
.BR -b ", " --bitmap=
.BR --grow .
The size can be given as
.B max
-which means to choose the largest size that fits all on all current drives.
+which means to choose the largest size that fits on all current drives.
.TP
.BR --assume-clean
really useful for Building RAID1 array. Only use this if you really
know what you are doing. This is currently only supported for --build.
+.TP
+.BR -N ", " --name=
+Set a
+.B name
+for the array. This is currently only effective when creating an
+array with a version-1 superblock. The name is a simple textual
+string that can be used to identify array components when assembling.
+
.TP
.BR -R ", " --run
Insist that
'standard' format, and the type and minor number will be determined
from this. See DEVICE NAMES below.
-The argumentment can also come immediately after
+The argument can also come immediately after
"-a". e.g. "-ap".
If
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
number based on that name. If the device name is not in one of these
-formats, then a unused minor number will be allocted. The minor
+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.
.M --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.
+
.TP
.BR -f ", " --force
Assemble the array even if some superblocks appear out-of-date
.BR sparc2.2 ,
.BR summaries ,
.BR resync ,
+.BR byteorder ,
or
.BR super-minor .
to perform a "resync" pass to make sure that all redundant information
is correct.
+The
+.B byteorder
+option allows arrays to be moved between machines with different
+byte-order.
+When assembling such an array for the first time after a move, giving
+.B "--update=byteorder"
+will cause
+.I mdadm
+to expect superblocks to have their byteorder reversed, and will
+correct that order before assembling the array. This is only valid
+with original (Verion 0.90) superblocks.
+
The
.B summaries
option will correct the summaries in the superblock. That is the
'''add, or
hotadd listed devices.
+.TP
+.BR --re-add
+Listed devices are assumed to have recently been part of the array,
+and they are re-added. This is only different from --add when a
+write-intent bitmap is present. It causes only those parts of the
+device that have changed since the device was removed from the array
+to be reconstructed.
+
+This flag is only needed with arrays that are built without a
+superblock (i.e. --build, not --create). For array with a superblock,
+.I mdadm
+checks if a superblock is present and automatically determines if a
+re-add is appropriate.
+
.TP
.BR -r ", " --remove
remove listed devices. They must not be active. i.e. they should
.TP
.B --sparc2.2
-In an array was created on a 2.2 Linux kernel patched with RAID
+If an array was created on a 2.2 Linux kernel patched with RAID
support, the superblock will have been created incorrectly, or at
least incompatibly with 2.4 and later kernels. Using the
.B --sparc2.2
.B NewArray
events and more significantly
.B DegradedArray
+and
+.B SparesMissing
events. Running
.in +5
.B " mdadm --monitor --scan -1"
.B TestMessage
alert for every array found at startup. This alert gets mailed and
passed to the alert program. This can be used for testing that alert
-message to get through successfully.
+message do get through successfully.
.SH ASSEMBLE MODE
is not given and insufficient drives were listed to start a complete
(non-degraded) array, then the array is not started (to guard against
usage errors). To insist that the array be started in this case (as
-may work for RAID1, 4, 5 or 6), give the
+may work for RAID1, 4, 5, 6, or 10), give the
.B --run
flag.
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
-string to the device name, with an intervening "_p" if the device name
+string to the device name, with an intervening "p" if the device name
ends with a digit.
The
.PP
This usage is similar to
.BR --create .
-The difference is that it creates a legacy array without a superblock. With
+The difference is that it creates an array without a superblock. With
these arrays there is no difference between initially creating the array and
subsequently assembling the array, except that hopefully there is useful
data there in the second case.
-The level may only be 0, raid0, or linear. All devices must be listed
-and the array will be started once complete.
+The level may raid0, linear, multipath, or faulty, or one of their
+synonyms. All devices must be listed and the array will be started
+once complete.
.SH CREATE MODE
This usage will initialise a new md array, associate some devices with
it, and activate the array.
-This the
+If the
.B --auto
option is given (as described in more detail in the section on
Assemble mode), then the md device will be created with a suitable
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 not spares.
+and if the destination array has a failed drive but no spares.
If any devices are listed on the command line,
.B mdadm
Various types of growth may be added during 2.6 development, possibly
including restructuring a raid5 array to have more active devices.
-Currently the only support available is to change the "size" attribute
-for arrays with redundancy, and the raid-disks attribute of RAID1
-arrays.
+Currently the only support available is to
+.IP \(bu 4
+change the "size" attribute
+for RAID1, RAID5 and RAID6.
+.IP \(bu 4
+change the "raid-disks" attribute of RAID1.
+.IP \(bu 4
+add a write-intent bitmap to a RAID1 array.
+.PP
-Normally when an array is build the "size" it taken from the smallest
+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
time, removed and replaced with larger drives, then you could have an
array of large drives with only a small amount used. In this
devices that which were in those slots must be failed and removed.
When the number of devices is increased, any hot spares that are
-present may be activated immediately.
+present will be activated immediately.
+
+A write-intent bitmap can be added to, or remove from, an active RAID1
+array. Either internal bitmap, of 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.
.SH EXAMPLES
.B mdadm
was previously known as
.BR mdctl .
-
+.P
+.B mdadm
+is completely separate from the
+.B 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:
.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
.PP
-for new releases of the RAID driver check out:
-
+The lastest version of
+.I mdadm
+should always be available from
.IP
-.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
-ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
+.UR http://www.kernel.org/pub/linux/utils/raid/mdadm/
+http://www.kernel.org/pub/linux/utils/raid/mdadm/
.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/
-.URk
-.PP
-.BR mdadm.conf (5),
-.BR md (4).
+.IR mdadm.conf (5),
+.IR md (4).
.PP
.IR raidtab (5),
.IR raid0run (8),
.IR raidstop (8),
-.IR mkraid (8)
+.IR mkraid (8).