From owner-freebsd-fs@FreeBSD.ORG  Sat Mar 26 14:42:58 2011
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Date: Sat, 26 Mar 2011 15:42:57 +0100
Message-ID: <AANLkTimzb0timUQTfokYga3DNCC_bONhCjyEUgf_eGsd@mail.gmail.com>
From: Anders Andersson <pipatron@gmail.com>
To: freebsd-fs@freebsd.org
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Subject: RAID-Z in a disk-failure.
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Evening! I have a question about ZFS in a FreeBSD setting, more
specifically about RAID-Z. I have never used ZFS so I might have
misunderstood something,  but imagine this situation:

You're using ZFS in RAID-Z with 4 disks. One of these gets a
catastrophic failure. You replace the disk with a new one, but when
the RAID-Z is rebuilt, the software notices that one sector/block on
another disk has become corrupted. It notices this because ZFS keeps a
checksum.

What happens then? Since the redundancy is temporarily disabled
because of the failed disk, this sector/block is nowhere to be found.
My hope is that the system will handle this gracefully, so that only
the file using this block will be unreadable, but the rest of the data
is available and can be rebuilt. The worst that could happen is that
the rebuild is refused and the whole pool is gone.

Have I missed something in this scenario?

// Anders