Message-ID: <4DDD0B91.9080300@2ndquadrant.com>
Date: Wed, 25 May 2011 10:00:49 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: =?UTF-8?B?R3J6ZWdvcnogSmHFm2tpZXdpY3o=?= <gryzman@gmail.com>
CC: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: serveRAID M5014 SAS
References: <BANLkTi=fE2YCS0Lra42ei1hFrKqXdVk2jA@mail.gmail.com>
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Grzegorz Jaśkiewicz wrote:
> Does anyone here have any bad experiences with the RAID card in subject ?
> This is in an IBM server, with 2.5" 10k drives.
>
> But we seem to observe its poor performance in other configurations as
> well (with different drives, different settings) in comparison with -
> say, what dell provides.
>   

Older ServeRAID cards have never been reported as very fast.  They were 
an OK controller if you just want to mirror a pair of drives or 
something simple like that.  Their performance on larger RAID arrays is 
terrible compared to the LSI products that Dell uses.

However, the M5014 *is* an LSI derived product, with a proper 
battery-backed write cache and everything.  I'm not sure if older views 
are even useful now.  Few things to check:

-Is the battery working, and the write cache set in write-back mode?
-Has read-ahead been set usefully?
-Did you try to use a more complicated RAID mode than this card can handle?

Those are the three easiest ways to trash performance here.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books