Reply-To: <gnanam@zoniac.com>
From: "Gnanakumar" <gnanam@zoniac.com>
To: <pgsql-admin@postgresql.org>
Subject: Postgresql shared_buffer and SHMMAX configuration
Date: Fri, 9 Jul 2010 17:00:45 +0530
Organization: Zoniac Software Private Limited
Message-ID: <01e201cb1f5a$2e3f01f0$8abd05d0$@com>
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Hi,

Recently we upgraded our production server RAM from 7.5GB to 15GB for the
following reasons:
	1. to solve performance issues
	2. the number of concurrent users increased from 150 to 300

Our production server is not a dedicated database server and is being shared
with our other application softwares like:
	1. Tomcat
	2. Apache
	3. Cron based scheduled programs
	4. Also few Java-based thread programs
all running in the same server. 

We are trying to configure postgresql parameters with 15GB RAM.

Linux
---------------
Kernal.SHMMAX 
	From - 2147483648
	To   - 19818063053

250kB + 8.2kB * shared_buffers + 14.2kB * max_connections
(250kB + 8.2kB * 2359296kB(2304*1024) + 14.2kB * 500) = 19353577.2 * 1024 =
19818063052.8

postgresql.conf
--------------------
shared_buffers 
	From - 1536MB
	To - 2304MB

Since we have other application also running we have taken 15% of the RAM
value for shared_buffers.

max_connection 
	From - 500
	To - 500

PGPOOL configuration
---------------------
num_init_children 
	From - 150
	To - 420
child_max_connections 
	From - 20
	To - 30

We have more than 300 Users accessing our server concurrently so we need
around 300 concurrent connections.

My questions are:
1) Is my tuning of PostgreSQL parameters to 15 GB RAM configuration correct?
Experts advice/recommendation on this are highly appreciated.
2) Will the above configuration improve the performance of the database
overall?

Thanks in advance

Regards
Gnanam