From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: pgsql-performance@postgresql.org
Subject: SSD and RAID
Date: Tue, 06 Mar 2012 11:37:25 +1300
Message-ID: <4F554025.9040101@catalyst.net.nz> (raw)
Where I work we are starting to look at using SSDs for database server
storage. Despite the higher per unit cost it is quite attractive to
replace 6-8 SAS drives in RAID 10 by a pair of SSD in RAID 1 that will
probably perform better and use less power.
Which brings up the question of should it be a pair in RAID 1 or just a
singe drive? Traditionally this would have been a no brainer "Of course
you want RAID 1 or RAID 10"! However our experience with SSD failure
modes points to firmware bugs as primary source of trouble - and these
are likely to impact both drives (nearly) simultaneously in a RAID 1
configuration. Also the other major issue to watch - flash write limit
exhaustion - is also likely to hit at the same time for a pair of drives
in RAID 1.
One option to get around the simultaneous firmware failure is to be to
get 2 *similar* drives from different manufactures (e.g OCZ Vertex 32
and Intel 520 - both Sandforce but different firmware setup). However
using different manufacturers drives is a pest (e.g different smart
codes maintained and/or different meanings for the same codes)
What are other folks who are using SSDs doing?
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: mark.kirkwood@catalyst.net.nz
Subject: Re: SSD and RAID
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