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-rw-r--r--Documentation/md.txt72
1 files changed, 68 insertions, 4 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt
index 4edd39ec7db9..188f4768f1d5 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -233,9 +233,9 @@ 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. At array creation it will
- default to 0, though starting the array as 'clean' will
- set it much larger.
+ 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.
new_dev
This file can be written but not read. The value written should
@@ -296,6 +296,51 @@ All md devices contain:
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.
+
+
+
As component devices are added to an md array, they appear in the 'md'
directory as new directories named
@@ -334,8 +379,9 @@ Each directory contains:
Writing "writemostly" sets the writemostly flag.
Writing "-writemostly" clears the writemostly flag.
Writing "blocked" sets the "blocked" flag.
- Writing "-blocked" clear the "blocked" flag and allows writes
+ Writing "-blocked" clears the "blocked" flag and allows writes
to complete.
+ Writing "in_sync" sets the in_sync flag.
This file responds to select/poll. Any change to 'faulty'
or 'blocked' causes an event.
@@ -372,6 +418,24 @@ Each directory contains:
array. If a value less than the current component_size is
written, it will be rejected.
+ recovery_start
+
+ 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 is will steadily increase, and if the recovery is
+ interrupted, restoring this value can cause recovery to
+ avoid repeating the earlier blocks. With v1.x metadata, this
+ value is saved and restored automatically.
+
+ 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.
+
+ Setting this to 'none' is equivalent to setting 'in_sync'.
+ Setting to any other value also clears the 'in_sync' flag.
+
+
An active md device will also contain and entry for each active device
in the array. These are named