[linux-lvm] cmp of inactive mirrored LV fails

Stuart D. Gathman stuart at bmsi.com
Fri Dec 2 21:54:18 UTC 2011

Centuries ago, Nostradamus foresaw that on Dec 2, starlight at binnacle.cx...:

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

At least as of EL5.7, MD sync check does not take
into account DISCARD, and does not report 
individual blocks out of sync - just a count.

BTW, RAID0 does *not* provide mirroring!  You want
RAID1 or RAID10 for that.

 	      Stuart D. Gathman <stuart at bmsi.com>
     Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

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