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Date:      Wed, 15 Apr 2020 09:28:02 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        d@delphij.net, freebsd-fs <freebsd-fs@freebsd.org>
Subject:   Re: zpool question -- resilvering doesn't fully check on-disk data for corruption?
Message-ID:  <9173c2f9-57be-b390-1941-0673ebc5ba9a@FreeBSD.org>
In-Reply-To: <bc5add51-3094-9e6b-1054-821ac18265a7@delphij.net>
References:  <bc5add51-3094-9e6b-1054-821ac18265a7@delphij.net>

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On 15/04/2020 09:03, Xin Li via freebsd-fs wrote:
> My understanding is that both resilver and scrub
> would read all data from a RAID-Z pool

Resilver differs from scrub in that it checks only blocks corresponding to
periods in dirty time log (DTL).  That is, if a disks becomes unavailable and
then comes back, a resilver will read only those blocks on other disks that are
necessary to write any missing blocks on the flaky disk.  If a disk gets
replaced then a resilver reads all blocks on remaining disks that are necessary
to re-create data on the replaced disk.
A scrub always reads all used blocks.

-- 
Andriy Gapon



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