From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gionatan Danti <g.danti@assyoma.it>
Subject: Re: Filesystem corruption on RAID1
Date: Mon, 21 Aug 2017 07:57:17 +0200
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To: Chris Murphy <lists@colorremedies.com>
Cc: Mikael Abrahamsson <swmike@swm.pp.se>, Roger Heflin <rogerheflin@gmail.com>, Wols Lists <antlists@youngman.org.uk>, Reindl Harald <h.reindl@thelounge.net>, Roman Mamedov <rm@romanrm.net>, Linux RAID <linux-raid@vger.kernel.org>, chris@colorremedies.com
List-Id: linux-raid.ids

Il 21-08-2017 01:22 Chris Murphy ha scritto:
> Another way is to split the mirror (make one device faulty), and then
> fix the remaining drive (now degraded). If that goes well, the 2nd
> device can be re-added. Here's a caveat thought: how it resync's will
> depend on the write-intent bitmap being present. I have no idea if
> write-intent bitmaps on two drives can get out of sync and what the
> ensuing behavior is, but I'd like to think md will discover the fixed
> drive event count is higher than the re-added one, and if necessary
> does a full resync, rather than possibly re-introducing any
> corruption.

On the corruption I am replicating (brief SATA power interruptions), the 
event count of both drives where identical, and so was the write bitmap 
(not always, thought).

To be 100% sure to completly copy from the mirror device, you had to 
re-add the corrupted driver as a spare, by using "--add-spare". From the 
man page:

"--add-spare
Add a device as a spare. This is similar to --add except that it does 
not attempt --re-add first. The device will be added as a spare even if 
it looks like it could be an recent member of the array."

Regards.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
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