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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:
233 233
234 resync_start 234 resync_start
235 The point at which resync should start. If no resync is needed, 235 The point at which resync should start. If no resync is needed,
236 this will be a very large number. At array creation it will 236 this will be a very large number (or 'none' since 2.6.30-rc1). At
237 default to 0, though starting the array as 'clean' will 237 array creation it will default to 0, though starting the array as
238 set it much larger. 238 'clean' will set it much larger.
239 239
240 new_dev 240 new_dev
241 This file can be written but not read. The value written should 241 This file can be written but not read. The value written should
@@ -296,6 +296,51 @@ All md devices contain:
296 active-idle 296 active-idle
297 like active, but no writes have been seen for a while (safe_mode_delay). 297 like active, but no writes have been seen for a while (safe_mode_delay).
298 298
299 bitmap/location
300 This indicates where the write-intent bitmap for the array is
301 stored.
302 It can be one of "none", "file" or "[+-]N".
303 "file" may later be extended to "file:/file/name"
304 "[+-]N" means that many sectors from the start of the metadata.
305 This is replicated on all devices. For arrays with externally
306 managed metadata, the offset is from the beginning of the
307 device.
308 bitmap/chunksize
309 The size, in bytes, of the chunk which will be represented by a
310 single bit. For RAID456, it is a portion of an individual
311 device. For RAID10, it is a portion of the array. For RAID1, it
312 is both (they come to the same thing).
313 bitmap/time_base
314 The time, in seconds, between looking for bits in the bitmap to
315 be cleared. In the current implementation, a bit will be cleared
316 between 2 and 3 times "time_base" after all the covered blocks
317 are known to be in-sync.
318 bitmap/backlog
319 When write-mostly devices are active in a RAID1, write requests
320 to those devices proceed in the background - the filesystem (or
321 other user of the device) does not have to wait for them.
322 'backlog' sets a limit on the number of concurrent background
323 writes. If there are more than this, new writes will by
324 synchronous.
325 bitmap/metadata
326 This can be either 'internal' or 'external'.
327 'internal' is the default and means the metadata for the bitmap
328 is stored in the first 256 bytes of the allocated space and is
329 managed by the md module.
330 'external' means that bitmap metadata is managed externally to
331 the kernel (i.e. by some userspace program)
332 bitmap/can_clear
333 This is either 'true' or 'false'. If 'true', then bits in the
334 bitmap will be cleared when the corresponding blocks are thought
335 to be in-sync. If 'false', bits will never be cleared.
336 This is automatically set to 'false' if a write happens on a
337 degraded array, or if the array becomes degraded during a write.
338 When metadata is managed externally, it should be set to true
339 once the array becomes non-degraded, and this fact has been
340 recorded in the metadata.
341
342
343
299 344
300As component devices are added to an md array, they appear in the 'md' 345As component devices are added to an md array, they appear in the 'md'
301directory as new directories named 346directory as new directories named
@@ -334,8 +379,9 @@ Each directory contains:
334 Writing "writemostly" sets the writemostly flag. 379 Writing "writemostly" sets the writemostly flag.
335 Writing "-writemostly" clears the writemostly flag. 380 Writing "-writemostly" clears the writemostly flag.
336 Writing "blocked" sets the "blocked" flag. 381 Writing "blocked" sets the "blocked" flag.
337 Writing "-blocked" clear the "blocked" flag and allows writes 382 Writing "-blocked" clears the "blocked" flag and allows writes
338 to complete. 383 to complete.
384 Writing "in_sync" sets the in_sync flag.
339 385
340 This file responds to select/poll. Any change to 'faulty' 386 This file responds to select/poll. Any change to 'faulty'
341 or 'blocked' causes an event. 387 or 'blocked' causes an event.
@@ -372,6 +418,24 @@ Each directory contains:
372 array. If a value less than the current component_size is 418 array. If a value less than the current component_size is
373 written, it will be rejected. 419 written, it will be rejected.
374 420
421 recovery_start
422
423 When the device is not 'in_sync', this records the number of
424 sectors from the start of the device which are known to be
425 correct. This is normally zero, but during a recovery
426 operation is will steadily increase, and if the recovery is
427 interrupted, restoring this value can cause recovery to
428 avoid repeating the earlier blocks. With v1.x metadata, this
429 value is saved and restored automatically.
430
431 This can be set whenever the device is not an active member of
432 the array, either before the array is activated, or before
433 the 'slot' is set.
434
435 Setting this to 'none' is equivalent to setting 'in_sync'.
436 Setting to any other value also clears the 'in_sync' flag.
437
438
375 439
376An active md device will also contain and entry for each active device 440An active md device will also contain and entry for each active device
377in the array. These are named 441in the array. These are named