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Re: [linux-lvm] Powerfailure and snapshot consistency

On Mon, 28 Mar 2011, Phillip Susi wrote:

On 3/27/2011 5:55 PM, Stuart D. Gathman wrote:
Don't need help, just trying to understand the event.  So from what you
said, the problem probably stems from the RAID1 resync, which could
make one PV "older" than the other.

The data is written to the primary mirror first, so this can't happen.
Proper use of barriers will prevent this whole scenario, so my guess is
that you are using ext3 ( which defaults to nobarrier ) or explicitly
mounting ext4 with nobarrier.

Ah, thank you!  Yes, I am using ext3 with EL5.5 defaults, and will now learn
about the barrier option.  Seems like a good thing to turn on when "replace
battery" comes up on the ups.

It sounds like dumb luck/divine mercy that the raid 1 PV on which the
production LV resides did not have a similar issue.

	      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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