For this reason, md will normally refuse to start such an array. This
requires the sysadmin to take action to explicitly start the array
-desipite 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
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
raid levels that involve striping (1,4,5,6,10). The address space
of the array is conceptually divided into chunks and consecutive
chunks are striped onto neighbouring devices.
- The size should be atleast PAGE_SIZE (4k) and should be a power
+ The size should be at least PAGE_SIZE (4k) and should be a power
of 2. This can only be set while assembling an array
component_size
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
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'.
+ 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.
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 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
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
(i.e. is a spare or has failed) or an integer less than the
- 'raid_disks' number for the array indicating which possition
+ '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.
rdNN
-where 'NN' is the possition 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,
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
Code Review / linux-2.6.git / blobdiff