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[linux-lvm] Powerfailure and snapshot consistency



At a production site, there was a power failure, and the UPS battery wasn't up to the job. There was a backup running, but otherwise things were quiet.

The production system came up fine, but the test system, which was running from a snapshot, had a corrupted filesystem. The PVs are md raid1. One of the PVs had to resync when power was restored.

My theory about what happened to the test system is this: the origin and snapshot were on different PVs. The origin was writing as part of the backup process, and some blocks that were supposed to be copied to the COW didn't get copied, but were written to the origin. This would result in
an inconsistent image for the snapshot.

Assuming my theory is correct, the morals would be:

1) don't run production on a snapshot :-)

2) make sure important LVs do not span multiple PVs (except for LVM
   mirroring) - you could be unhappy in the event of a system crash.

While I can peruse lvdisplay --maps manually, is there a tool that highlights LVs that span multiple PVs?

--
	      Stuart D. Gathman <stuart 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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