Re: PostgreSQL Performance on OpenBSD

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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