diff options
author | NeilBrown <neilb@suse.de> | 2009-12-13 20:49:56 -0500 |
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committer | NeilBrown <neilb@suse.de> | 2009-12-13 20:51:41 -0500 |
commit | ece5cff0da9e696c360fff592cb5f51b6419e4d6 (patch) | |
tree | 1c5cab0e89ae466be9edb476ceb91e5c898fafa6 /Documentation | |
parent | 624ce4f5658fa3e0303c1217bba2706142fe7568 (diff) |
md: Support write-intent bitmaps with externally managed metadata.
In this case, the metadata needs to not be in the same
sector as the bitmap.
md will not read/write any bitmap metadata. Config must be
done via sysfs and when a recovery makes the array non-degraded
again, writing 'true' to 'bitmap/can_clear' will allow bits in
the bitmap to be cleared again.
Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/md.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/md.txt b/Documentation/md.txt index 18fad6876228..21d26fb5d02b 100644 --- a/Documentation/md.txt +++ b/Documentation/md.txt | |||
@@ -322,6 +322,22 @@ All md devices contain: | |||
322 | 'backlog' sets a limit on the number of concurrent background | 322 | 'backlog' sets a limit on the number of concurrent background |
323 | writes. If there are more than this, new writes will by | 323 | writes. If there are more than this, new writes will by |
324 | synchronous. | 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. | ||
325 | 341 | ||
326 | 342 | ||
327 | 343 | ||