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Re: Scaling concerns

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: tsuraan <tsuraan(at)gmail(dot)com>
Cc: "Greg Smith" <gsmith(at)gregsmith(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Scaling concerns
Date: 2006-12-18 04:59:12
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Lists: pgsql-performance
tsuraan <tsuraan(at)gmail(dot)com> writes:
> Is the WAL at the same location as the xlog (transaction log?)?

Same thing.

> The checkpoint_segments doc says increasing that value is really only
> useful if the xlog is separate from the data,

Dunno where you read that, but it's utter bilge.  If you've got a
write-intensive workload, you want to crank checkpoint_segments as high
as you can stand.  With the default settings on a modern machine it's
not hard at all to push it into checkpointing every dozen or seconds,
which will completely kill performance.  (Disk space for pg_xlog/ and
potential delay during crash restart are the only negatives here.  If
you are willing to push the average inter-checkpoint interval past five
minutes then you need to increase checkpoint_timeout too.)

			regards, tom lane

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