Re: wal_buffers

On Oct 5, 2005, at 8:23 AM, Ian Westmacott wrote:

> Can anyone tell me what precisely a WAL buffer contains,
> so that I can compute an appropriate setting for
> wal_buffers (in 8.0.3)?
>
> I know the documentation suggests there is little
> evidence that supports increasing wal_buffers, but we
> are inserting a large amount of data that, I believe,
> easily exceeds the default 64K in a single transaction.
> We are also very sensitive to write latency.
>
> As background, we are doing a sustained insert of 2.2
> billion rows in 1.3 million transactions per day.  Thats
> about 1700 rows per transaction, at (roughly) 50 bytes
> per row.

Ian,

The WAL Configuration chapter (25.2) has a pretty good discussion of
how wal_buffers is used:

http://www.postgresql.org/docs/8.0/static/wal-configuration.html

You might also take a look at Josh Berkus' recent testing on this
setting:

http://www.powerpostgresql.com/

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Thomas F. O'Connell
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