[mythtv-users] Reassemble RAID with mdadm

[Steve Hodge]

On Wed, Mar 17, 2010 at 11:45 AM, Graham Mitchell <gmitch at woodlea.com>wrote:

> > With 4 drives you would be better using RAID 0+1
>
>
> Probably better off using RAID 1+0 (a stripe of mirrors), rather than 0+1
> (a
> mirror of a stripe)
>

Yes. Just to elaborate, the difference is in what happens when you lose a
drive. With raid 0+1 if you lose a drive you lose the entire stripe - you're
effectively back to a raid 0. With raid 1+0 if you lose a drive you've got
one degraded mirrored pair but the rest of the mirrors in the stripe are
still at full performance. However it's possible that mdadm is actually
smart enough to handle these two cases identically anyway (but I'm not 100%
sure).

With mdadm you'd be better off using raid10 which manages striping and
mirroring together at the block level. It's both more flexible and
potentially better performing. Basically it spreads X copies of the data
over Y drives with the copies staggered physically. Look it up on wikipedia
for more details.

Cheers,
Steve
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