Re: High update activity, PostgreSQL vs BigDBMS

On Fri, 29 Dec 2006, Alvaro Herrera wrote:

> Ron wrote:
>
>> C= What file system are you using?  Unlike BigDBMS, pg does not have
>> its own native one, so you have to choose the one that best suits
>> your needs.  For update heavy applications involving lots of small
>> updates jfs and XFS should both be seriously considered.
>
> Actually it has been suggested that a combination of ext2 (for WAL) and
> ext3 (for data, with data journalling disabled) is a good performer.
> AFAIK you don't want the overhead of journalling for the WAL partition.

When benchmarking various options for a new PG server at one of my clients, I
tried ext2 and ext3 (data=writeback) for the WAL and it appeared to be fastest
to have ext2 for the WAL.  The winning time was 157m46.713s for ext2,
159m47.098s for combined ext3 data/xlog and 158m25.822s for ext3
data=writeback.  This was on an 8x150GB Raptor RAID10 on an Areca 1130 w/ 1GB
BBU cache.  This config benched out faster than a 6disk RAID10 + 2 disk RAID1
for those of you who have been wondering if the BBU write back cache mitigates
the need for separate WAL (at least on this workload).  Those are the fastest
times for each config, but ext2 WAL was always faster than the other two
options.  I didn't test any other filesystems in this go around.

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