[linux-lvm] cmp of inactive mirrored LV fails

starlight at binnacle.cx starlight at binnacle.cx
Fri Dec 2 21:14:44 UTC 2011

By coincidence I've just setup my first MD
RAID0 partitions on a different system.

   echo "check" >>/sys/block/md?/md/sync_action

which triggers a mirror check.  I'm guessing that
this operation takes account of the DISCARD
discrepencies and therefore does not report
false errors.  (correct me if I'm wrong)

Does LVM have anything similar to this feature?

At 04:01 PM 12/2/2011 -0500, Stuart D. Gathman wrote:
>This is not necessarily a bug.  Both MD and LVM support
>DISCARD, and discarded blocks are not necessarily synced
>between mirror legs.  The same thing happens with MD,
>and the MD "cmp" operation reports the number of blocks
>out of sync, but not which blocks!  (So LVM is actually
>an improvement on that score.)  Swap volumes make
>heavy use of DISCARD and are especially likely to
>have blocks out of sync.

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