Re: Sizing and striping log area

On 13 Oct 2002 at 16:26, Brett wrote:
>Forgive my ignorance, but what should I consider when sizing the partition
>which houses the pg_xlog area? Are logs cleared out every once in awhile
>or do they continue to accumulate? Let's say your DB is around 4 GB,
>what should the log area size be, or does the size of the DB not matter,
>if not which factors should be considered?

Well, you know the exact size of pg_xlogs in advance. It's 16MB*number of WAL
files. So for 40 WAL files in postgresql.conf, you get 640MB of pg_xlog.

Yes, they are recycled. So they don't grow beyond this size. But from
performance point of view, what's important is to put them on separate drive,
much better on separate IO channel.

>Now straying even further from the original subject... Would hardware vs
>software RAID 0 not make a difference in reality? Software striping

You can try. People here have come up with figures that indicate that it does
not make difference. But software RAID requires bit more BW as OS has to send
data to different drives by itself. But software RAID is easier to upgrade and
doesn't cost much in terms of CPU. Take your pick..

HTH

Bye
Shridhar

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