Date: Thu, 03 Aug 2006 05:39:56 -0400
From: Michael Stone <mstone+postgres@mathom.us>
Subject: Re: XFS filessystem for Datawarehousing
In-reply-to: 
 <F5F602C218633C419C7BCA6CDDC6E90A0248B0A8@COSSMGMBX04.EMAIL.CORP.TLD>
To: pgsql-performance@postgresql.org
Mail-followup-to: pgsql-performance@postgresql.org
Message-id: <20060803093953.GP2900@mathom.us>
MIME-version: 1.0
Content-type: text/plain; charset=us-ascii; format=flowed
Content-disposition: inline
References: 
 <F5F602C218633C419C7BCA6CDDC6E90A0248B0A8@COSSMGMBX04.EMAIL.CORP.TLD>
User-Agent: Mutt/1.5.12-2006-07-14

On Thu, Aug 03, 2006 at 01:10:39AM -0600, Koth, Christian (DWBI) wrote:
>For what reason are you planning to use a journaling FS? I think using WAL, fsyncing every transaction and using a journaling FS is tautologous. And if you have problems using EXT2 you can just add the journal later without loosing data.
>My tests using EXT2 showed a performance boost up to 50% on INSERTs.

The requirements for the WAL filesystem and for the data filesystem are 
different. Having the WAL on a small ext2 filesystem makes sense and is 
good for performance. Having the data on a huge ext2 filesystem is a 
horrible idea, because you'll fsck forever if there's a crash, and 
because ext2 isn't a great performer for large filesystems. I typically 
have a couple-gig ext2 WAL paired with a couple of couple-hundred-gig 
xfs data & index partitions. Note that the guarantees of a journaling fs 
like xfs have nothing to do with the kind of journaling done by the WAL, 
and each has its place on a postgres system.

Mike Stone