Re: LAPP server moving from 4 GB RAM to 16 GB - increase shared_buffers?

On Tue, Oct 4, 2011 at 11:11 AM, Alexander Farber <
alexander(dot)farber(at)gmail(dot)com> wrote:

> Hello,
>
> I run a LAPP server (PostgreSQL 8.4 @ CentOS 5.7 / 64 bit;
> only 4 GB RAM) with the following config:
>
> postgresql.conf (unix socket only and - ):
>
> max_connections = 50
> shared_buffers = 1024MB # min 128kB
>
> pgbouncer.ini:
>
> [databases]
> pref = host=/tmp user=XXX password=XXX dbname=XXX
>
> [pgbouncer]
> logfile = /var/log/pgbouncer.log
> pidfile = /var/run/pgbouncer/pgbouncer.pid
> listen_port = 6432
> unix_socket_dir = /tmp
>
> auth_type = md5
> auth_file = /var/lib/pgsql/data/global/pg_auth
>
> pool_mode = session
> server_reset_query = DISCARD ALL;
>
> server_check_delay = 10
> max_client_conn = 200
> default_pool_size = 16
>
> and httpd.conf (running Drupal 7 + custom PHP scripts,
> non-persistent, with mostly "select" queries):
>
> <IfModule prefork.c>
> StartServers 8
> MinSpareServers 5
> MaxSpareServers 20
> ServerLimit 120
> MaxClients 120
> MaxRequestsPerChild 4000
> </IfModule>
>
> It works ok, but now users have collected some money and
> I've purchased a better server with 16 GB and CentOS 6 /64 bit.
>
> I understand, that my question is naive, but on the other side
> even if I provide more information, will that really help? -
>
> My question is: should I increase shared_buffers
> from 1024MB to 8192MB, does it make any sense?
>
> Thank you
> Alex
>
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You'd want to increase shared_buffers to take advantage of the extra memory,
but I'm not sure if you'd want to use 50% of the system's memory. For a
server running other services, I'd suggest keeping shared_buffers at 25% or
less. Linux will allocate the unused RAM for disk cache
fairly aggressively on its own, so you'll have a performance boost for both
Postgres and PHP/Apache with the extra memory.

-Adam Cornett