Re: Testing Sandforce SSD

From: Yeb Havinga <yebhavinga(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: Testing Sandforce SSD
Date: 2010-07-28 13:45:23
Message-ID: 4C503473.5080105@gmail.com
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Michael Stone wrote:
> On Mon, Jul 26, 2010 at 03:23:20PM -0600, Greg Spiegelberg wrote:
>> I know I'm talking development now but is there a case for a pg_xlog
>> block
>> device to remove the file system overhead and guaranteeing your data is
>> written sequentially every time?
>
> If you dedicate a partition to xlog, you already get that in practice
> with no extra devlopment.
Due to the LBA remapping of the SSD, I'm not sure of putting files that
are sequentially written in a different partition (together with e.g.
tables) would make a difference: in the end the SSD will have a set new
blocks in it's buffer and somehow arrange them into sets of 128KB of
256KB writes for the flash chips. See also
http://www.anandtech.com/show/2899/2

But I ran out of ideas to test, so I'm going to test it anyway.

regards,
Yeb Havinga

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