From mboxrd@z Thu Jan  1 00:00:00 1970
From: Billy Crook <billycrook@gmail.com>
Subject: Re: max number of devices in raid6 array
Date: Wed, 12 Aug 2009 11:27:51 -0500
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To: Goswin von Brederlow <goswin-v-b@web.de>
Cc: David Cure <lnk@cure.nom.fr>, John Robinson <john.robinson@anonymous.org.uk>, linux-raid@vger.kernel.org
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On Wed, Aug 12, 2009 at 09:53, Goswin von Brederlow<goswin-v-b@web.de> wrote:
> With how many devices does the MTBFS of
> a raid6 drop below that of a single disk?

Four devices.

The more important thing to worry about is running in to an
uncorrectable error during rebuild, twice during the same rebuild.
I'd say a good rule of thumb is no more than 8TB in a RAID5 array;
16TB in a raid6 array if you want to remain very safe.  YMMV.  Your
risk comfort and willingness to restore from backups will vary as
well.