Re: Upgrade to dual processor machine? - Mailing list pgsql-general

Hello Shridhar,

thanks for your answer...

1) in the docs it says: shared_buffers should be 2*max_connections, min 16.
now, you suggest to put it to 500-600 MB, which means I will have to
increase shared_buffers to 68683 -- is this really correct? I mean,
RAM is allready now almost totally consumed.

2) the database has a size of 3.6 GB at the moment... about 100 user tables.

3) ok, I understand: I am not creating any indexes usually. Only once at night
all user indexes are dropped and recreated, I could imagine to increase the
sort_mem for this script... so sort_mem with 1024K is ok, or should it be
lowered to, say, 512K ?


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----- Original Message -----
From: "Shridhar Daithankar" <shridhar_daithankar@persistent.co.in>
To: <pgsql-general@postgresql.org>
Sent: Wednesday, November 13, 2002 8:53 AM
Subject: Re: [GENERAL] Upgrade to dual processor machine?


> On 13 Nov 2002 at 8:29, Henrik Steffen wrote:
>
> > Hello Josh!
> >
> > This is was I figured out now:
> >
> > 1) RAM available: 1024 MB, there's nothing else but postgres on this
> >    machine, so if I calculate 128 MB for Linux, there are 896 MB left
> >    for Postgres.
> >
> > 2) 70 % of 896 MB is 627 MB
> >
> > Now, if I follow your instructions:
> >
> > 250K +
> > 8.2K * 128 (shared_buffers) = 1049,6K +
> > 14.2K * 64 (max_connections) = 908,8K +
> > 1024K * 5000 (average number of requests per minute) = 5120000K
> > ===============================================================
> > 5122208.4K ==> 5002.16 MB
> >
> > this is a little bit more than I have available, isn't it? :(((
>
> Obviously tuning depends upon application and you have to set the threshold by
> trial and error.
>
> I would suggest following from some recent discussions on such topics.
>
> 1)Set shared buffers somewhere between 500-600MB. Tha'ts going to be optimal
> range for a Gig of RAM.
>
> 2) How big you database is? How much of it you need it in memory at any given
> time? You need to get these figures while setting shared buffers. But still 500-
> 600MB seems good because it does not include file system cache and buffers.
>
> 3) Sort mem is a tricky affair. AFAIU, it is used only when you create index or
> sort results of a query. If do these things seldomly, you can set this very low
> or default. For individual session that creates index, you can set the sort
> memory accordingly. Certainly in your case, number of requests per minute are
> high but if you are not creating any index/sorting in each query, you can leave
> the default as it is..
>
> HTH
>
> Bye
>  Shridhar
>
> --
> Another dream that failed.  There's nothing sadder. -- Kirk, "This side of
> Paradise", stardate 3417.3
>
>
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