Re: configuration problems

Henk,

> I have some problems configuring postgresql 7.0 . I am using the
> rpms
> on a redhat 7.1 distribution. I want to change the option -N to 64
> and
> the -B to 128. I put this in the postmaster.opts.default file but
> when
> I restart postgresql and I take a look at the status, it uses N=32
> and
> B=64. Is there something I should know that isn't in the
> documentation
> ? Can there be something wrong with the standard RedHat scripts to
> start the server ?

Three things:
1. If you are concerned about performance, you should upgrade. There
are a score of performance improvements made between ver. 7.0.2 and
7.1.3.
2. Rather than modifying the Postmaster.opts.default file, you should
be
modifying postgresql.conf. (in ...pgsql/data/). If the two confilct,
postgresql.conf will override postmaster.opts.default.
3. I have no idea what's in your startup script, but it's entirely
possible that Red Hat decided to "help you" by specifying parameters in
the startup file. You'll need to read the script yourself to make sure.
It's most likely located in /etc/init.d/

> Also, what is the best way to make an estimation of the highest
> number
> of connections my system will be able to handle ? (the server is a
> PIII
> 500MHz with 256MB RAM).

Well, the highest number of connections is waht you set in the
postgresql.conf file. The highest number that's a good idea depends on
too many vague factors to answer on a mailing list:
1. Is the server running any other major applications? Apache?
X-Windows?
2. Check the memory consumption of just the kernel running my itself,
and any applications from #1.
3. What will users be doing on your server? Simple queries? Complex
queries? Long-running procedures?
4. How fast is your disk access? Can you afford to go to swap?
5. Do you have seperate disks for the OS and lof files and datatbase,
or
is everything on the same HDD?
6. How large are your tables?
7. How often can you VACUUM?
etc.

As an example of the lack of easy answers, I have a 500mhz
Celeron/256mb/IDE. As well as postgres, it's running PHP and Apache.
To increase efficiency, I added a second IDE drive for the log files.
On most things in my application, it can support up to 10 users without
showing noticable lag, and 20 with some slowness. However, there are
two operations -- one really complex search query, and one long
function
involving lots of Updates -- that if more than 3 users do them at once,
the whole system slows down to a crawl, expecially if it's been a while
since the last VACUUM.

-Josh

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