All md devices contain:
level
- a text file indicating the 'raid level'. This may be a standard
- numerical level prefixed by "RAID-" - e.g. "RAID-5", or some
- other name such as "linear" or "multipath".
+ 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), this file will be empty.
+ 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.
raid_disks
a text file with a simple number indicating the number of devices
1.2 (newer format in varying locations) or "none" indicating that
the kernel isn't managing metadata at all.
- level
- The raid 'level' for this array. The name will often (but not
- always) be the same as the name of the module that implements the
- level. To be auto-loaded the module must have an alias
- md-$LEVEL e.g. md-raid5
- This can be written only while the array is being assembled, not
- after it is started.
+ layout
+ 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.
+
+ resync_start
+ The point at which resync should start. If no resync is needed,
+ this will be a very large number. At array creation it will
+ default to 0, though starting the array as 'clean' will
+ set it much larger.
new_dev
This file can be written but not read. The value written should
available. It will then appear at md/dev-XXX (depending on the
name of the device) and further configuration is then possible.
+ 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 arrive, the array is marked as 'dirty' before the write
+ commenses. 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.
+
+ array_state
+ This file contains a single word which describes the current
+ state of the array. In many cases, the state can be set by
+ writing the word for the desired state, however some states
+ cannot be explicitly set, and some transitions are not allowed.
+
+ 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
+ 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
+ read-auto
+ like readonly, but behaves like 'clean' on a write request.
+
+ 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 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.
+
+ active-idle
+ like active, but no writes have been seen for a while (safe_mode_delay).
+
+
sync_speed_min
sync_speed_max
This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
faulty - device has been kicked from active use due to
a detected fault
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.
spare - device is working, but not a full member.
This includes spares that are in the process
of being recoverred to
This list make 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.
errors
An approximate count of read errors that have been detected on
than sectors, this my be larger than the number of actual errors
by a factor of the number of sectors in a page.
+ bitmap_set_bits
+ If the array has a write-intent bitmap, then writing to this
+ attribute can set bits in the bitmap, indicating that a resync
+ 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.
+ They should be scaled by the bitmap_chunksize.
+
Each active md device may also have attributes specific to the
personality module that manages it.
These are specific to the implementation of the module and could