|
@@ -1,42 +1,77 @@
|
|
|
-Tools that manage md devices can be found at
|
|
|
- http://www.kernel.org/pub/linux/utils/raid/
|
|
|
-
|
|
|
+RAID arrays
|
|
|
+===========
|
|
|
|
|
|
Boot time assembly of RAID arrays
|
|
|
---------------------------------
|
|
|
|
|
|
+Tools that manage md devices can be found at
|
|
|
+ http://www.kernel.org/pub/linux/utils/raid/
|
|
|
+
|
|
|
+
|
|
|
You can boot with your md device with the following kernel command
|
|
|
lines:
|
|
|
|
|
|
-for old raid arrays without persistent superblocks:
|
|
|
+for old raid arrays without persistent superblocks::
|
|
|
+
|
|
|
md=<md device no.>,<raid level>,<chunk size factor>,<fault level>,dev0,dev1,...,devn
|
|
|
|
|
|
-for raid arrays with persistent superblocks
|
|
|
+for raid arrays with persistent superblocks::
|
|
|
+
|
|
|
md=<md device no.>,dev0,dev1,...,devn
|
|
|
-or, to assemble a partitionable array:
|
|
|
+
|
|
|
+or, to assemble a partitionable array::
|
|
|
+
|
|
|
md=d<md device no.>,dev0,dev1,...,devn
|
|
|
-
|
|
|
-md device no. = the number of the md device ...
|
|
|
- 0 means md0,
|
|
|
- 1 md1,
|
|
|
- 2 md2,
|
|
|
- 3 md3,
|
|
|
- 4 md4
|
|
|
-
|
|
|
-raid level = -1 linear mode
|
|
|
- 0 striped mode
|
|
|
- other modes are only supported with persistent super blocks
|
|
|
-
|
|
|
-chunk size factor = (raid-0 and raid-1 only)
|
|
|
- Set the chunk size as 4k << n.
|
|
|
-
|
|
|
-fault level = totally ignored
|
|
|
-
|
|
|
-dev0-devn: e.g. /dev/hda1,/dev/hdc1,/dev/sda1,/dev/sdb1
|
|
|
-
|
|
|
-A possible loadlin line (Harald Hoyer <HarryH@Royal.Net>) looks like this:
|
|
|
-
|
|
|
-e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro
|
|
|
+
|
|
|
+``md device no.``
|
|
|
++++++++++++++++++
|
|
|
+
|
|
|
+The number of the md device
|
|
|
+
|
|
|
+================= =========
|
|
|
+``md device no.`` device
|
|
|
+================= =========
|
|
|
+ 0 md0
|
|
|
+ 1 md1
|
|
|
+ 2 md2
|
|
|
+ 3 md3
|
|
|
+ 4 md4
|
|
|
+================= =========
|
|
|
+
|
|
|
+``raid level``
|
|
|
+++++++++++++++
|
|
|
+
|
|
|
+level of the RAID array
|
|
|
+
|
|
|
+=============== =============
|
|
|
+``raid level`` level
|
|
|
+=============== =============
|
|
|
+-1 linear mode
|
|
|
+0 striped mode
|
|
|
+=============== =============
|
|
|
+
|
|
|
+other modes are only supported with persistent super blocks
|
|
|
+
|
|
|
+``chunk size factor``
|
|
|
++++++++++++++++++++++
|
|
|
+
|
|
|
+(raid-0 and raid-1 only)
|
|
|
+
|
|
|
+Set the chunk size as 4k << n.
|
|
|
+
|
|
|
+``fault level``
|
|
|
++++++++++++++++
|
|
|
+
|
|
|
+Totally ignored
|
|
|
+
|
|
|
+``dev0`` to ``devn``
|
|
|
+++++++++++++++++++++
|
|
|
+
|
|
|
+e.g. ``/dev/hda1``, ``/dev/hdc1``, ``/dev/sda1``, ``/dev/sdb1``
|
|
|
+
|
|
|
+A possible loadlin line (Harald Hoyer <HarryH@Royal.Net>) looks like this::
|
|
|
+
|
|
|
+ e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro
|
|
|
|
|
|
|
|
|
Boot time autodetection of RAID arrays
|
|
@@ -45,10 +80,10 @@ Boot time autodetection of RAID arrays
|
|
|
When md is compiled into the kernel (not as module), partitions of
|
|
|
type 0xfd are scanned and automatically assembled into RAID arrays.
|
|
|
This autodetection may be suppressed with the kernel parameter
|
|
|
-"raid=noautodetect". As of kernel 2.6.9, only drives with a type 0
|
|
|
+``raid=noautodetect``. As of kernel 2.6.9, only drives with a type 0
|
|
|
superblock can be autodetected and run at boot time.
|
|
|
|
|
|
-The kernel parameter "raid=partitionable" (or "raid=part") means
|
|
|
+The kernel parameter ``raid=partitionable`` (or ``raid=part``) means
|
|
|
that all auto-detected arrays are assembled as partitionable.
|
|
|
|
|
|
Boot time assembly of degraded/dirty arrays
|
|
@@ -56,22 +91,23 @@ Boot time assembly of degraded/dirty arrays
|
|
|
|
|
|
If a raid5 or raid6 array is both dirty and degraded, it could have
|
|
|
undetectable data corruption. This is because the fact that it is
|
|
|
-'dirty' means that the parity cannot be trusted, and the fact that it
|
|
|
+``dirty`` means that the parity cannot be trusted, and the fact that it
|
|
|
is degraded means that some datablocks are missing and cannot reliably
|
|
|
be reconstructed (due to no parity).
|
|
|
|
|
|
For this reason, md will normally refuse to start such an array. This
|
|
|
requires the sysadmin to take action to explicitly start the array
|
|
|
-despite possible corruption. This is normally done with
|
|
|
+despite possible corruption. This is normally done with::
|
|
|
+
|
|
|
mdadm --assemble --force ....
|
|
|
|
|
|
This option is not really available if the array has the root
|
|
|
filesystem on it. In order to support this booting from such an
|
|
|
-array, md supports a module parameter "start_dirty_degraded" which,
|
|
|
+array, md supports a module parameter ``start_dirty_degraded`` which,
|
|
|
when set to 1, bypassed the checks and will allows dirty degraded
|
|
|
arrays to be started.
|
|
|
|
|
|
-So, to boot with a root filesystem of a dirty degraded raid[56], use
|
|
|
+So, to boot with a root filesystem of a dirty degraded raid 5 or 6, use::
|
|
|
|
|
|
md-mod.start_dirty_degraded=1
|
|
|
|
|
@@ -80,30 +116,30 @@ Superblock formats
|
|
|
------------------
|
|
|
|
|
|
The md driver can support a variety of different superblock formats.
|
|
|
-Currently, it supports superblock formats "0.90.0" and the "md-1" format
|
|
|
+Currently, it supports superblock formats ``0.90.0`` and the ``md-1`` format
|
|
|
introduced in the 2.5 development series.
|
|
|
|
|
|
The kernel will autodetect which format superblock is being used.
|
|
|
|
|
|
-Superblock format '0' is treated differently to others for legacy
|
|
|
+Superblock format ``0`` is treated differently to others for legacy
|
|
|
reasons - it is the original superblock format.
|
|
|
|
|
|
|
|
|
General Rules - apply for all superblock formats
|
|
|
------------------------------------------------
|
|
|
|
|
|
-An array is 'created' by writing appropriate superblocks to all
|
|
|
+An array is ``created`` by writing appropriate superblocks to all
|
|
|
devices.
|
|
|
|
|
|
-It is 'assembled' by associating each of these devices with an
|
|
|
+It is ``assembled`` by associating each of these devices with an
|
|
|
particular md virtual device. Once it is completely assembled, it can
|
|
|
be accessed.
|
|
|
|
|
|
An array should be created by a user-space tool. This will write
|
|
|
superblocks to all devices. It will usually mark the array as
|
|
|
-'unclean', or with some devices missing so that the kernel md driver
|
|
|
-can create appropriate redundancy (copying in raid1, parity
|
|
|
-calculation in raid4/5).
|
|
|
+``unclean``, or with some devices missing so that the kernel md driver
|
|
|
+can create appropriate redundancy (copying in raid 1, parity
|
|
|
+calculation in raid 4/5).
|
|
|
|
|
|
When an array is assembled, it is first initialized with the
|
|
|
SET_ARRAY_INFO ioctl. This contains, in particular, a major and minor
|
|
@@ -126,13 +162,12 @@ Devices that have failed or are not yet active can be detached from an
|
|
|
array using HOT_REMOVE_DISK.
|
|
|
|
|
|
|
|
|
-Specific Rules that apply to format-0 super block arrays, and
|
|
|
- arrays with no superblock (non-persistent).
|
|
|
--------------------------------------------------------------
|
|
|
+Specific Rules that apply to format-0 super block arrays, and arrays with no superblock (non-persistent)
|
|
|
+--------------------------------------------------------------------------------------------------------
|
|
|
|
|
|
-An array can be 'created' by describing the array (level, chunksize
|
|
|
-etc) in a SET_ARRAY_INFO ioctl. This must have major_version==0 and
|
|
|
-raid_disks != 0.
|
|
|
+An array can be ``created`` by describing the array (level, chunksize
|
|
|
+etc) in a SET_ARRAY_INFO ioctl. This must have ``major_version==0`` and
|
|
|
+``raid_disks != 0``.
|
|
|
|
|
|
Then uninitialized devices can be added with ADD_NEW_DISK. The
|
|
|
structure passed to ADD_NEW_DISK must specify the state of the device
|
|
@@ -142,24 +177,26 @@ Once started with RUN_ARRAY, uninitialized spares can be added with
|
|
|
HOT_ADD_DISK.
|
|
|
|
|
|
|
|
|
-
|
|
|
MD devices in sysfs
|
|
|
-------------------
|
|
|
-md devices appear in sysfs (/sys) as regular block devices,
|
|
|
-e.g.
|
|
|
+
|
|
|
+md devices appear in sysfs (``/sys``) as regular block devices,
|
|
|
+e.g.::
|
|
|
+
|
|
|
/sys/block/md0
|
|
|
|
|
|
-Each 'md' device will contain a subdirectory called 'md' which
|
|
|
+Each ``md`` device will contain a subdirectory called ``md`` which
|
|
|
contains further md-specific information about the device.
|
|
|
|
|
|
All md devices contain:
|
|
|
+
|
|
|
level
|
|
|
- a text file indicating the 'raid level'. e.g. raid0, raid1,
|
|
|
+ a text file indicating the ``raid level``. e.g. raid0, raid1,
|
|
|
raid5, linear, multipath, faulty.
|
|
|
If no raid level has been set yet (array is still being
|
|
|
assembled), the value will reflect whatever has been written
|
|
|
to it, which may be a name like the above, or may be a number
|
|
|
- such as '0', '5', etc.
|
|
|
+ such as ``0``, ``5``, etc.
|
|
|
|
|
|
raid_disks
|
|
|
a text file with a simple number indicating the number of devices
|
|
@@ -172,10 +209,10 @@ All md devices contain:
|
|
|
A change to this attribute will not be permitted if it would
|
|
|
reduce the size of the array. To reduce the number of drives
|
|
|
in an e.g. raid5, the array size must first be reduced by
|
|
|
- setting the 'array_size' attribute.
|
|
|
+ setting the ``array_size`` attribute.
|
|
|
|
|
|
chunk_size
|
|
|
- This is the size in bytes for 'chunks' and is only relevant to
|
|
|
+ This is the size in bytes for ``chunks`` and is only relevant to
|
|
|
raid levels that involve striping (0,4,5,6,10). The address space
|
|
|
of the array is conceptually divided into chunks and consecutive
|
|
|
chunks are striped onto neighbouring devices.
|
|
@@ -183,7 +220,7 @@ All md devices contain:
|
|
|
of 2. This can only be set while assembling an array
|
|
|
|
|
|
layout
|
|
|
- The "layout" for the array for the particular level. This is
|
|
|
+ The ``layout`` for the array for the particular level. This is
|
|
|
simply a number that is interpretted differently by different
|
|
|
levels. It can be written while assembling an array.
|
|
|
|
|
@@ -193,22 +230,24 @@ All md devices contain:
|
|
|
devices. Writing a number (in Kilobytes) which is less than
|
|
|
the available size will set the size. Any reconfiguration of the
|
|
|
array (e.g. adding devices) will not cause the size to change.
|
|
|
- Writing the word 'default' will cause the effective size of the
|
|
|
+ Writing the word ``default`` will cause the effective size of the
|
|
|
array to be whatever size is actually available based on
|
|
|
- 'level', 'chunk_size' and 'component_size'.
|
|
|
+ ``level``, ``chunk_size`` and ``component_size``.
|
|
|
|
|
|
This can be used to reduce the size of the array before reducing
|
|
|
the number of devices in a raid4/5/6, or to support external
|
|
|
metadata formats which mandate such clipping.
|
|
|
|
|
|
reshape_position
|
|
|
- This is either "none" or a sector number within the devices of
|
|
|
- the array where "reshape" is up to. If this is set, the three
|
|
|
+ This is either ``none`` or a sector number within the devices of
|
|
|
+ the array where ``reshape`` is up to. If this is set, the three
|
|
|
attributes mentioned above (raid_disks, chunk_size, layout) can
|
|
|
potentially have 2 values, an old and a new value. If these
|
|
|
- values differ, reading the attribute returns
|
|
|
+ values differ, reading the attribute returns::
|
|
|
+
|
|
|
new (old)
|
|
|
- and writing will effect the 'new' value, leaving the 'old'
|
|
|
+
|
|
|
+ and writing will effect the ``new`` value, leaving the ``old``
|
|
|
unchanged.
|
|
|
|
|
|
component_size
|
|
@@ -223,9 +262,9 @@ All md devices contain:
|
|
|
metadata_version
|
|
|
This indicates the format that is being used to record metadata
|
|
|
about the array. It can be 0.90 (traditional format), 1.0, 1.1,
|
|
|
- 1.2 (newer format in varying locations) or "none" indicating that
|
|
|
+ 1.2 (newer format in varying locations) or ``none`` indicating that
|
|
|
the kernel isn't managing metadata at all.
|
|
|
- Alternately it can be "external:" followed by a string which
|
|
|
+ Alternately it can be ``external:`` followed by a string which
|
|
|
is set by user-space. This indicates that metadata is managed
|
|
|
by a user-space program. Any device failure or other event that
|
|
|
requires a metadata update will cause array activity to be
|
|
@@ -233,9 +272,9 @@ All md devices contain:
|
|
|
|
|
|
resync_start
|
|
|
The point at which resync should start. If no resync is needed,
|
|
|
- this will be a very large number (or 'none' since 2.6.30-rc1). At
|
|
|
+ this will be a very large number (or ``none`` since 2.6.30-rc1). At
|
|
|
array creation it will default to 0, though starting the array as
|
|
|
- 'clean' will set it much larger.
|
|
|
+ ``clean`` will set it much larger.
|
|
|
|
|
|
new_dev
|
|
|
This file can be written but not read. The value written should
|
|
@@ -246,10 +285,10 @@ All md devices contain:
|
|
|
|
|
|
safe_mode_delay
|
|
|
When an md array has seen no write requests for a certain period
|
|
|
- of time, it will be marked as 'clean'. When another write
|
|
|
- request arrives, the array is marked as 'dirty' before the write
|
|
|
- commences. This is known as 'safe_mode'.
|
|
|
- The 'certain period' is controlled by this file which stores the
|
|
|
+ of time, it will be marked as ``clean``. When another write
|
|
|
+ request arrives, the array is marked as ``dirty`` before the write
|
|
|
+ commences. This is known as ``safe_mode``.
|
|
|
+ The ``certain period`` is controlled by this file which stores the
|
|
|
period as a number of seconds. The default is 200msec (0.200).
|
|
|
Writing a value of 0 disables safemode.
|
|
|
|
|
@@ -260,38 +299,50 @@ All md devices contain:
|
|
|
cannot be explicitly set, and some transitions are not allowed.
|
|
|
|
|
|
Select/poll works on this file. All changes except between
|
|
|
- active_idle and active (which can be frequent and are not
|
|
|
- very interesting) are notified. active->active_idle is
|
|
|
- reported if the metadata is externally managed.
|
|
|
+ Active_idle and active (which can be frequent and are not
|
|
|
+ very interesting) are notified. active->active_idle is
|
|
|
+ reported if the metadata is externally managed.
|
|
|
|
|
|
clear
|
|
|
No devices, no size, no level
|
|
|
+
|
|
|
Writing is equivalent to STOP_ARRAY ioctl
|
|
|
+
|
|
|
inactive
|
|
|
May have some settings, but array is not active
|
|
|
- all IO results in error
|
|
|
+ all IO results in error
|
|
|
+
|
|
|
When written, doesn't tear down array, but just stops it
|
|
|
+
|
|
|
suspended (not supported yet)
|
|
|
All IO requests will block. The array can be reconfigured.
|
|
|
+
|
|
|
Writing this, if accepted, will block until array is quiessent
|
|
|
+
|
|
|
readonly
|
|
|
no resync can happen. no superblocks get written.
|
|
|
- write requests fail
|
|
|
+
|
|
|
+ Write requests fail
|
|
|
+
|
|
|
read-auto
|
|
|
- like readonly, but behaves like 'clean' on a write request.
|
|
|
+ like readonly, but behaves like ``clean`` on a write request.
|
|
|
+
|
|
|
+ clean
|
|
|
+ no pending writes, but otherwise active.
|
|
|
|
|
|
- clean - no pending writes, but otherwise active.
|
|
|
When written to inactive array, starts without resync
|
|
|
+
|
|
|
If a write request arrives then
|
|
|
- if metadata is known, mark 'dirty' and switch to 'active'.
|
|
|
- if not known, block and switch to write-pending
|
|
|
+ if metadata is known, mark ``dirty`` and switch to ``active``.
|
|
|
+ if not known, block and switch to write-pending
|
|
|
+
|
|
|
If written to an active array that has pending writes, then fails.
|
|
|
active
|
|
|
fully active: IO and resync can be happening.
|
|
|
When written to inactive array, starts with resync
|
|
|
|
|
|
write-pending
|
|
|
- clean, but writes are blocked waiting for 'active' to be written.
|
|
|
+ clean, but writes are blocked waiting for ``active`` to be written.
|
|
|
|
|
|
active-idle
|
|
|
like active, but no writes have been seen for a while (safe_mode_delay).
|
|
@@ -299,57 +350,71 @@ All md devices contain:
|
|
|
bitmap/location
|
|
|
This indicates where the write-intent bitmap for the array is
|
|
|
stored.
|
|
|
- It can be one of "none", "file" or "[+-]N".
|
|
|
- "file" may later be extended to "file:/file/name"
|
|
|
- "[+-]N" means that many sectors from the start of the metadata.
|
|
|
- This is replicated on all devices. For arrays with externally
|
|
|
- managed metadata, the offset is from the beginning of the
|
|
|
- device.
|
|
|
+
|
|
|
+ It can be one of ``none``, ``file`` or ``[+-]N``.
|
|
|
+ ``file`` may later be extended to ``file:/file/name``
|
|
|
+ ``[+-]N`` means that many sectors from the start of the metadata.
|
|
|
+
|
|
|
+ This is replicated on all devices. For arrays with externally
|
|
|
+ managed metadata, the offset is from the beginning of the
|
|
|
+ device.
|
|
|
+
|
|
|
bitmap/chunksize
|
|
|
The size, in bytes, of the chunk which will be represented by a
|
|
|
single bit. For RAID456, it is a portion of an individual
|
|
|
device. For RAID10, it is a portion of the array. For RAID1, it
|
|
|
is both (they come to the same thing).
|
|
|
+
|
|
|
bitmap/time_base
|
|
|
The time, in seconds, between looking for bits in the bitmap to
|
|
|
be cleared. In the current implementation, a bit will be cleared
|
|
|
- between 2 and 3 times "time_base" after all the covered blocks
|
|
|
+ between 2 and 3 times ``time_base`` after all the covered blocks
|
|
|
are known to be in-sync.
|
|
|
+
|
|
|
bitmap/backlog
|
|
|
When write-mostly devices are active in a RAID1, write requests
|
|
|
to those devices proceed in the background - the filesystem (or
|
|
|
other user of the device) does not have to wait for them.
|
|
|
- 'backlog' sets a limit on the number of concurrent background
|
|
|
+ ``backlog`` sets a limit on the number of concurrent background
|
|
|
writes. If there are more than this, new writes will by
|
|
|
synchronous.
|
|
|
+
|
|
|
bitmap/metadata
|
|
|
- This can be either 'internal' or 'external'.
|
|
|
- 'internal' is the default and means the metadata for the bitmap
|
|
|
- is stored in the first 256 bytes of the allocated space and is
|
|
|
- managed by the md module.
|
|
|
- 'external' means that bitmap metadata is managed externally to
|
|
|
- the kernel (i.e. by some userspace program)
|
|
|
+ This can be either ``internal`` or ``external``.
|
|
|
+
|
|
|
+ ``internal``
|
|
|
+ is the default and means the metadata for the bitmap
|
|
|
+ is stored in the first 256 bytes of the allocated space and is
|
|
|
+ managed by the md module.
|
|
|
+
|
|
|
+ ``external``
|
|
|
+ means that bitmap metadata is managed externally to
|
|
|
+ the kernel (i.e. by some userspace program)
|
|
|
+
|
|
|
bitmap/can_clear
|
|
|
- This is either 'true' or 'false'. If 'true', then bits in the
|
|
|
+ This is either ``true`` or ``false``. If ``true``, then bits in the
|
|
|
bitmap will be cleared when the corresponding blocks are thought
|
|
|
- to be in-sync. If 'false', bits will never be cleared.
|
|
|
- This is automatically set to 'false' if a write happens on a
|
|
|
+ to be in-sync. If ``false``, bits will never be cleared.
|
|
|
+ This is automatically set to ``false`` if a write happens on a
|
|
|
degraded array, or if the array becomes degraded during a write.
|
|
|
When metadata is managed externally, it should be set to true
|
|
|
once the array becomes non-degraded, and this fact has been
|
|
|
recorded in the metadata.
|
|
|
-
|
|
|
-
|
|
|
-
|
|
|
|
|
|
-As component devices are added to an md array, they appear in the 'md'
|
|
|
-directory as new directories named
|
|
|
+
|
|
|
+
|
|
|
+
|
|
|
+As component devices are added to an md array, they appear in the ``md``
|
|
|
+directory as new directories named::
|
|
|
+
|
|
|
dev-XXX
|
|
|
-where XXX is a name that the kernel knows for the device, e.g. hdb1.
|
|
|
+
|
|
|
+where ``XXX`` is a name that the kernel knows for the device, e.g. hdb1.
|
|
|
Each directory contains:
|
|
|
|
|
|
block
|
|
|
- a symlink to the block device in /sys/block, e.g.
|
|
|
+ a symlink to the block device in /sys/block, e.g.::
|
|
|
+
|
|
|
/sys/block/md0/md/dev-hdb1/block -> ../../../../block/hdb/hdb1
|
|
|
|
|
|
super
|
|
@@ -358,51 +423,83 @@ Each directory contains:
|
|
|
|
|
|
state
|
|
|
A file recording the current state of the device in the array
|
|
|
- which can be a comma separated list of
|
|
|
- faulty - device has been kicked from active use due to
|
|
|
- a detected fault, or it has unacknowledged bad
|
|
|
- blocks
|
|
|
- in_sync - device is a fully in-sync member of the array
|
|
|
- writemostly - device will only be subject to read
|
|
|
- requests if there are no other options.
|
|
|
- This applies only to raid1 arrays.
|
|
|
- blocked - device has failed, and the failure hasn't been
|
|
|
- acknowledged yet by the metadata handler.
|
|
|
- Writes that would write to this device if
|
|
|
- it were not faulty are blocked.
|
|
|
- spare - device is working, but not a full member.
|
|
|
- This includes spares that are in the process
|
|
|
- of being recovered to
|
|
|
- write_error - device has ever seen a write error.
|
|
|
- want_replacement - device is (mostly) working but probably
|
|
|
- should be replaced, either due to errors or
|
|
|
- due to user request.
|
|
|
- replacement - device is a replacement for another active
|
|
|
- device with same raid_disk.
|
|
|
+ which can be a comma separated list of:
|
|
|
+
|
|
|
+ faulty
|
|
|
+ device has been kicked from active use due to
|
|
|
+ a detected fault, or it has unacknowledged bad
|
|
|
+ blocks
|
|
|
+
|
|
|
+ in_sync
|
|
|
+ device is a fully in-sync member of the array
|
|
|
+
|
|
|
+ writemostly
|
|
|
+ device will only be subject to read
|
|
|
+ requests if there are no other options.
|
|
|
+
|
|
|
+ This applies only to raid1 arrays.
|
|
|
+
|
|
|
+ blocked
|
|
|
+ device has failed, and the failure hasn't been
|
|
|
+ acknowledged yet by the metadata handler.
|
|
|
+
|
|
|
+ Writes that would write to this device if
|
|
|
+ it were not faulty are blocked.
|
|
|
+
|
|
|
+ spare
|
|
|
+ device is working, but not a full member.
|
|
|
+
|
|
|
+ This includes spares that are in the process
|
|
|
+ of being recovered to
|
|
|
+
|
|
|
+ write_error
|
|
|
+ device has ever seen a write error.
|
|
|
+
|
|
|
+ want_replacement
|
|
|
+ device is (mostly) working but probably
|
|
|
+ should be replaced, either due to errors or
|
|
|
+ due to user request.
|
|
|
+
|
|
|
+ replacement
|
|
|
+ device is a replacement for another active
|
|
|
+ device with same raid_disk.
|
|
|
|
|
|
|
|
|
This list may grow in future.
|
|
|
+
|
|
|
This can be written to.
|
|
|
- Writing "faulty" simulates a failure on the device.
|
|
|
- Writing "remove" removes the device from the array.
|
|
|
- Writing "writemostly" sets the writemostly flag.
|
|
|
- Writing "-writemostly" clears the writemostly flag.
|
|
|
- Writing "blocked" sets the "blocked" flag.
|
|
|
- Writing "-blocked" clears the "blocked" flags and allows writes
|
|
|
- to complete and possibly simulates an error.
|
|
|
- Writing "in_sync" sets the in_sync flag.
|
|
|
- Writing "write_error" sets writeerrorseen flag.
|
|
|
- Writing "-write_error" clears writeerrorseen flag.
|
|
|
- Writing "want_replacement" is allowed at any time except to a
|
|
|
- replacement device or a spare. It sets the flag.
|
|
|
- Writing "-want_replacement" is allowed at any time. It clears
|
|
|
- the flag.
|
|
|
- Writing "replacement" or "-replacement" is only allowed before
|
|
|
- starting the array. It sets or clears the flag.
|
|
|
-
|
|
|
-
|
|
|
- This file responds to select/poll. Any change to 'faulty'
|
|
|
- or 'blocked' causes an event.
|
|
|
+
|
|
|
+ Writing ``faulty`` simulates a failure on the device.
|
|
|
+
|
|
|
+ Writing ``remove`` removes the device from the array.
|
|
|
+
|
|
|
+ Writing ``writemostly`` sets the writemostly flag.
|
|
|
+
|
|
|
+ Writing ``-writemostly`` clears the writemostly flag.
|
|
|
+
|
|
|
+ Writing ``blocked`` sets the ``blocked`` flag.
|
|
|
+
|
|
|
+ Writing ``-blocked`` clears the ``blocked`` flags and allows writes
|
|
|
+ to complete and possibly simulates an error.
|
|
|
+
|
|
|
+ Writing ``in_sync`` sets the in_sync flag.
|
|
|
+
|
|
|
+ Writing ``write_error`` sets writeerrorseen flag.
|
|
|
+
|
|
|
+ Writing ``-write_error`` clears writeerrorseen flag.
|
|
|
+
|
|
|
+ Writing ``want_replacement`` is allowed at any time except to a
|
|
|
+ replacement device or a spare. It sets the flag.
|
|
|
+
|
|
|
+ Writing ``-want_replacement`` is allowed at any time. It clears
|
|
|
+ the flag.
|
|
|
+
|
|
|
+ Writing ``replacement`` or ``-replacement`` is only allowed before
|
|
|
+ starting the array. It sets or clears the flag.
|
|
|
+
|
|
|
+
|
|
|
+ This file responds to select/poll. Any change to ``faulty``
|
|
|
+ or ``blocked`` causes an event.
|
|
|
|
|
|
errors
|
|
|
An approximate count of read errors that have been detected on
|
|
@@ -417,9 +514,9 @@ Each directory contains:
|
|
|
|
|
|
slot
|
|
|
This gives the role that the device has in the array. It will
|
|
|
- either be 'none' if the device is not active in the array
|
|
|
+ either be ``none`` if the device is not active in the array
|
|
|
(i.e. is a spare or has failed) or an integer less than the
|
|
|
- 'raid_disks' number for the array indicating which position
|
|
|
+ ``raid_disks`` number for the array indicating which position
|
|
|
it currently fills. This can only be set while assembling an
|
|
|
array. A device for which this is set is assumed to be working.
|
|
|
|
|
@@ -437,7 +534,7 @@ Each directory contains:
|
|
|
written, it will be rejected.
|
|
|
|
|
|
recovery_start
|
|
|
- When the device is not 'in_sync', this records the number of
|
|
|
+ When the device is not ``in_sync``, this records the number of
|
|
|
sectors from the start of the device which are known to be
|
|
|
correct. This is normally zero, but during a recovery
|
|
|
operation it will steadily increase, and if the recovery is
|
|
@@ -447,21 +544,21 @@ Each directory contains:
|
|
|
|
|
|
This can be set whenever the device is not an active member of
|
|
|
the array, either before the array is activated, or before
|
|
|
- the 'slot' is set.
|
|
|
+ the ``slot`` is set.
|
|
|
+
|
|
|
+ Setting this to ``none`` is equivalent to setting ``in_sync``.
|
|
|
+ Setting to any other value also clears the ``in_sync`` flag.
|
|
|
|
|
|
- Setting this to 'none' is equivalent to setting 'in_sync'.
|
|
|
- Setting to any other value also clears the 'in_sync' flag.
|
|
|
-
|
|
|
bad_blocks
|
|
|
This gives the list of all known bad blocks in the form of
|
|
|
start address and length (in sectors respectively). If output
|
|
|
is too big to fit in a page, it will be truncated. Writing
|
|
|
- "sector length" to this file adds new acknowledged (i.e.
|
|
|
+ ``sector length`` to this file adds new acknowledged (i.e.
|
|
|
recorded to disk safely) bad blocks.
|
|
|
|
|
|
unacknowledged_bad_blocks
|
|
|
This gives the list of known-but-not-yet-saved-to-disk bad
|
|
|
- blocks in the same form of 'bad_blocks'. If output is too big
|
|
|
+ blocks in the same form of ``bad_blocks``. If output is too big
|
|
|
to fit in a page, it will be truncated. Writing to this file
|
|
|
adds bad blocks without acknowledging them. This is largely
|
|
|
for testing.
|
|
@@ -469,16 +566,18 @@ Each directory contains:
|
|
|
|
|
|
|
|
|
An active md device will also contain an entry for each active device
|
|
|
-in the array. These are named
|
|
|
+in the array. These are named::
|
|
|
|
|
|
rdNN
|
|
|
|
|
|
-where 'NN' is the position in the array, starting from 0.
|
|
|
+where ``NN`` is the position in the array, starting from 0.
|
|
|
So for a 3 drive array there will be rd0, rd1, rd2.
|
|
|
-These are symbolic links to the appropriate 'dev-XXX' entry.
|
|
|
-Thus, for example,
|
|
|
+These are symbolic links to the appropriate ``dev-XXX`` entry.
|
|
|
+Thus, for example::
|
|
|
+
|
|
|
cat /sys/block/md*/md/rd*/state
|
|
|
-will show 'in_sync' on every line.
|
|
|
+
|
|
|
+will show ``in_sync`` on every line.
|
|
|
|
|
|
|
|
|
|
|
@@ -488,50 +587,62 @@ also have
|
|
|
sync_action
|
|
|
a text file that can be used to monitor and control the rebuild
|
|
|
process. It contains one word which can be one of:
|
|
|
- resync - redundancy is being recalculated after unclean
|
|
|
- shutdown or creation
|
|
|
- recover - a hot spare is being built to replace a
|
|
|
- failed/missing device
|
|
|
- idle - nothing is happening
|
|
|
- check - A full check of redundancy was requested and is
|
|
|
- happening. This reads all blocks and checks
|
|
|
- them. A repair may also happen for some raid
|
|
|
- levels.
|
|
|
- repair - A full check and repair is happening. This is
|
|
|
- similar to 'resync', but was requested by the
|
|
|
- user, and the write-intent bitmap is NOT used to
|
|
|
- optimise the process.
|
|
|
+
|
|
|
+ resync
|
|
|
+ redundancy is being recalculated after unclean
|
|
|
+ shutdown or creation
|
|
|
+
|
|
|
+ recover
|
|
|
+ a hot spare is being built to replace a
|
|
|
+ failed/missing device
|
|
|
+
|
|
|
+ idle
|
|
|
+ nothing is happening
|
|
|
+ check
|
|
|
+ A full check of redundancy was requested and is
|
|
|
+ happening. This reads all blocks and checks
|
|
|
+ them. A repair may also happen for some raid
|
|
|
+ levels.
|
|
|
+
|
|
|
+ repair
|
|
|
+ A full check and repair is happening. This is
|
|
|
+ similar to ``resync``, but was requested by the
|
|
|
+ user, and the write-intent bitmap is NOT used to
|
|
|
+ optimise the process.
|
|
|
|
|
|
This file is writable, and each of the strings that could be
|
|
|
read are meaningful for writing.
|
|
|
|
|
|
- 'idle' will stop an active resync/recovery etc. There is no
|
|
|
- guarantee that another resync/recovery may not be automatically
|
|
|
- started again, though some event will be needed to trigger
|
|
|
- this.
|
|
|
- 'resync' or 'recovery' can be used to restart the
|
|
|
- corresponding operation if it was stopped with 'idle'.
|
|
|
- 'check' and 'repair' will start the appropriate process
|
|
|
- providing the current state is 'idle'.
|
|
|
+ ``idle`` will stop an active resync/recovery etc. There is no
|
|
|
+ guarantee that another resync/recovery may not be automatically
|
|
|
+ started again, though some event will be needed to trigger
|
|
|
+ this.
|
|
|
+
|
|
|
+ ``resync`` or ``recovery`` can be used to restart the
|
|
|
+ corresponding operation if it was stopped with ``idle``.
|
|
|
+
|
|
|
+ ``check`` and ``repair`` will start the appropriate process
|
|
|
+ providing the current state is ``idle``.
|
|
|
|
|
|
This file responds to select/poll. Any important change in the value
|
|
|
triggers a poll event. Sometimes the value will briefly be
|
|
|
- "recover" if a recovery seems to be needed, but cannot be
|
|
|
- achieved. In that case, the transition to "recover" isn't
|
|
|
+ ``recover`` if a recovery seems to be needed, but cannot be
|
|
|
+ achieved. In that case, the transition to ``recover`` isn't
|
|
|
notified, but the transition away is.
|
|
|
|
|
|
degraded
|
|
|
This contains a count of the number of devices by which the
|
|
|
- arrays is degraded. So an optimal array will show '0'. A
|
|
|
- single failed/missing drive will show '1', etc.
|
|
|
+ arrays is degraded. So an optimal array will show ``0``. A
|
|
|
+ single failed/missing drive will show ``1``, etc.
|
|
|
+
|
|
|
This file responds to select/poll, any increase or decrease
|
|
|
in the count of missing devices will trigger an event.
|
|
|
|
|
|
mismatch_count
|
|
|
- When performing 'check' and 'repair', and possibly when
|
|
|
- performing 'resync', md will count the number of errors that are
|
|
|
- found. The count in 'mismatch_cnt' is the number of sectors
|
|
|
- that were re-written, or (for 'check') would have been
|
|
|
+ When performing ``check`` and ``repair``, and possibly when
|
|
|
+ performing ``resync``, md will count the number of errors that are
|
|
|
+ found. The count in ``mismatch_cnt`` is the number of sectors
|
|
|
+ that were re-written, or (for ``check``) would have been
|
|
|
re-written. As most raid levels work in units of pages rather
|
|
|
than sectors, this may be larger than the number of actual errors
|
|
|
by a factor of the number of sectors in a page.
|
|
@@ -542,27 +653,30 @@ also have
|
|
|
would need to check the corresponding blocks. Either individual
|
|
|
numbers or start-end pairs can be written. Multiple numbers
|
|
|
can be separated by a space.
|
|
|
- Note that the numbers are 'bit' numbers, not 'block' numbers.
|
|
|
+
|
|
|
+ Note that the numbers are ``bit`` numbers, not ``block`` numbers.
|
|
|
They should be scaled by the bitmap_chunksize.
|
|
|
|
|
|
- sync_speed_min
|
|
|
- sync_speed_max
|
|
|
- This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
|
|
|
+ sync_speed_min, sync_speed_max
|
|
|
+ This are similar to ``/proc/sys/dev/raid/speed_limit_{min,max}``
|
|
|
however they only apply to the particular array.
|
|
|
- If no value has been written to these, or if the word 'system'
|
|
|
+
|
|
|
+ If no value has been written to these, or if the word ``system``
|
|
|
is written, then the system-wide value is used. If a value,
|
|
|
in kibibytes-per-second is written, then it is used.
|
|
|
+
|
|
|
When the files are read, they show the currently active value
|
|
|
- followed by "(local)" or "(system)" depending on whether it is
|
|
|
+ followed by ``(local)`` or ``(system)`` depending on whether it is
|
|
|
a locally set or system-wide value.
|
|
|
|
|
|
sync_completed
|
|
|
This shows the number of sectors that have been completed of
|
|
|
whatever the current sync_action is, followed by the number of
|
|
|
sectors in total that could need to be processed. The two
|
|
|
- numbers are separated by a '/' thus effectively showing one
|
|
|
+ numbers are separated by a ``/`` thus effectively showing one
|
|
|
value, a fraction of the process that is complete.
|
|
|
- A 'select' on this attribute will return when resync completes,
|
|
|
+
|
|
|
+ A ``select`` on this attribute will return when resync completes,
|
|
|
when it reaches the current sync_max (below) and possibly at
|
|
|
other times.
|
|
|
|
|
@@ -570,26 +684,24 @@ also have
|
|
|
This shows the current actual speed, in K/sec, of the current
|
|
|
sync_action. It is averaged over the last 30 seconds.
|
|
|
|
|
|
- suspend_lo
|
|
|
- suspend_hi
|
|
|
+ suspend_lo, suspend_hi
|
|
|
The two values, given as numbers of sectors, indicate a range
|
|
|
within the array where IO will be blocked. This is currently
|
|
|
only supported for raid4/5/6.
|
|
|
|
|
|
- sync_min
|
|
|
- sync_max
|
|
|
+ sync_min, sync_max
|
|
|
The two values, given as numbers of sectors, indicate a range
|
|
|
- within the array where 'check'/'repair' will operate. Must be
|
|
|
- a multiple of chunk_size. When it reaches "sync_max" it will
|
|
|
+ within the array where ``check``/``repair`` will operate. Must be
|
|
|
+ a multiple of chunk_size. When it reaches ``sync_max`` it will
|
|
|
pause, rather than complete.
|
|
|
- You can use 'select' or 'poll' on "sync_completed" to wait for
|
|
|
+ You can use ``select`` or ``poll`` on ``sync_completed`` to wait for
|
|
|
that number to reach sync_max. Then you can either increase
|
|
|
- "sync_max", or can write 'idle' to "sync_action".
|
|
|
+ ``sync_max``, or can write ``idle`` to ``sync_action``.
|
|
|
|
|
|
- The value of 'max' for "sync_max" effectively disables the limit.
|
|
|
+ The value of ``max`` for ``sync_max`` effectively disables the limit.
|
|
|
When a resync is active, the value can only ever be increased,
|
|
|
never decreased.
|
|
|
- The value of '0' is the minimum for "sync_min".
|
|
|
+ The value of ``0`` is the minimum for ``sync_min``.
|
|
|
|
|
|
|
|
|
|
|
@@ -598,13 +710,15 @@ personality module that manages it.
|
|
|
These are specific to the implementation of the module and could
|
|
|
change substantially if the implementation changes.
|
|
|
|
|
|
-These currently include
|
|
|
+These currently include:
|
|
|
|
|
|
stripe_cache_size (currently raid5 only)
|
|
|
number of entries in the stripe cache. This is writable, but
|
|
|
there are upper and lower limits (32768, 17). Default is 256.
|
|
|
+
|
|
|
strip_cache_active (currently raid5 only)
|
|
|
number of active entries in the stripe cache
|
|
|
+
|
|
|
preread_bypass_threshold (currently raid5 only)
|
|
|
number of times a stripe requiring preread will be bypassed by
|
|
|
a stripe that does not require preread. For fairness defaults
|