I'm pretty sure sort buffer is measured in k, not 8k units. i.e.
16384 sort mem is 16 Megs.
Or are you referring to something other than sort_mem?
On Thu, 15 May 2003, Martin Foster wrote:
> http://www.postgresql.org/docs/aw_pgsql_book/hw_performance/0.html
>
> I was taking a look at the above document, and found it very
> interesting. Essentially, it talks about two very important
> configuration features being the Cache and Sort sizes.
>
> Now, I was wondering how accurate it is when looking at this.
> Essentially, the author recommends using 25% of the available RAM for
> the cache and 2-4% for the sort buffer. Since units are available in
> 8K units, the numbers seem to come across as a bit high for a machine
> with 512Megs, dedicated to the PostgreSQL server.
>
> For example a conversion of Megabytes to Kilobytes then to 8K units:
> 128 x 1024 / 8 = 16384 (Cache)
> 20 x 1024 / 8 = 2560 (Sort)
>
> My database has a lot of information that is being queried over and over
> due to the fact that it's running a web based application. So for me,
> a large cache makes sense as it will allow information to be queried
> without the associated expensive I/O.
>
> However are the above numbers realistic? This would require some
> fairly customized kernels for OpenBSD to allow for numbers that high as
> well? And what about the Write Ahead Log (WAL) would a number close to
> 20-64 megs seem as realistic and proper?
>
> Martin Foster
> Creator/Designer Ethereal Realms
> martin@ethereal-realms.org
>
>
>
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