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Date: Sun, 9 Jan 2011 20:01:59 +1100
Message-ID: <AANLkTikn2G_23M3PbERTo8KR3sDqxkhWr=OntA4cVwh9@mail.gmail.com>
From: Jean-Yves Avenard <jyavenard@gmail.com>
To: Matthew Seaman <m.seaman@infracaninophile.co.uk>
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Cc: freebsd-stable@freebsd.org
Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks
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Hi

On 9 January 2011 19:44, Matthew Seaman <m.seaman@infracaninophile.co.uk> wrote:
> Not without backing up your current data, destroying the existing
> zpool(s) and rebuilding from scratch.
>
> Note: raidz2 on 4 disks doesn't really win you anything over 2 x mirror
> pairs of disks, and the RAID10 mirror is going to be rather more performant.

I would have thought that the probability of failure to be slightly different.
Sure you out of 4 disks, 2 can fail in both conditions.

*But*, in raidz2, any two of the four can fail.
In RAID10, the two disks that failed must be in different block
otherwise you loose it all

As such the resilience for failure in a RAIDz2 is far greater than in
a RAID10 system