- 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, of 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
- 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
- value, a fraction of the process that is complete.
-
- sync_speed
- This shows the current actual speed, in K/sec, of the current
- sync_action. It is averaged over the last 30 seconds.
-
+ 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
+ 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.
+
+ 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.
+
+ 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).
+
+ 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.
+ 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
+ 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
+ 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)
+ bitmap/can_clear
+ 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
+ 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.
+
+
+