Re: LAPP server moving from 4 GB RAM to 16 GB - increase shared_buffers? - Mailing list pgsql-general

From Adam Cornett
Subject Re: LAPP server moving from 4 GB RAM to 16 GB - increase shared_buffers?
Date
Msg-id CAB5sPxajHfffuw1RCoc3OUY9xXfNDa1VE3DdvENMndNxOqJC4w@mail.gmail.com
Whole thread Raw
In response to LAPP server moving from 4 GB RAM to 16 GB - increase shared_buffers?  (Alexander Farber <alexander.farber@gmail.com>)
List pgsql-general

On Tue, Oct 4, 2011 at 11:11 AM, Alexander Farber <alexander.farber@gmail.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

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