Re: Advice configuring ServeRAID 8k for performance

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Scott Carey <scott(at)richrelevance(dot)com>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, Kenneth Cox <kenstir(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Advice configuring ServeRAID 8k for performance
Date: 2010-08-17 01:31:25
Message-ID: 201008170131.o7H1VPc26427@momjian.us
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Scott Carey wrote:
> Don't ever have WAL and data on the same OS volume as ext3.
>
> If data=writeback, performance will be fine, data integrity will be ok
> for WAL, but data integrity will not be sufficient for the data
> partition. If data=ordered, performance will be very bad, but data
> integrity will be OK.
>
> This is because an fsync on ext3 flushes _all dirty pages in the file
> system_ to disk, not just those for the file being fsync'd.
>
> One partition for WAL, one for data. If using ext3 this is essentially
> a performance requirement no matter how your array is set up underneath.

Do we need to document this?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

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