Message-ID: <4DDE0E77.6070804@catalyst.net.nz>
Date: Thu, 26 May 2011 20:25:27 +1200
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
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CC: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: serveRAID M5014 SAS
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On 26/05/11 20:11, Grzegorz Jaśkiewicz wrote:
> The card is configured in 1+0 . with 128k stripe afaik (I'm a
> developer, we don't have hardware guys here).
> Are you's sure about the lack of cache by default on the card ? I
> thought the difference is that 5104 has 256, and 5105 has 512 ram
> already on it.

No, I'm not sure about what the default is for the M5014 - I'd recommend 
checking this with your supplier (or looking at the invoice if you can 
get it). My *feeling* is that you may have 256M cache but no battery kit 
- as this is an optional part - so the the card will not got into 
writeback mode if that is the case.

FWIW - we got our best (pgbench) results with 256K stripe, No (card) 
readahead and hyperthreading off on the host.

You can interrogate the config of the card and the raid 10 array using 
the megaraid cli package - you need to read the (frankly terrible) 
manual to discover which switches to use to determine battery and cache 
status etc. If you email me privately I'll get you a link to the 
relevant docs!

Cheers

Mark