On 11/30/2012 09:44 AM, Niels Kristian Schjødt wrote:
Just a note on your iostat numbers. The first reading is actually just a summary. You want the subsequent readings.
The pgsql_tmp dir is not changing at all it's constantly empty (a size of 4.0K).
Good.
Filesystem 1K-blocks Used Available Use% Mounted on /dev/md3 230619228 5483796 213420620 3% /ssd
Good. You could just be seeing lots of genuine activity. But going back on the thread, I remember seeing this in your postgresql.conf: shared_buffers = 7680MB Change this to: shared_buffers = 4GB I say that because you mentioned you're using Ubuntu 12.04, and we were having some problems with PG on that platform. With shared_buffers over 4GB, it starts doing really weird things to the memory subsystem. Whatever it does causes the kernel to purge cache rather aggressively. We saw a 60% reduction in read IO by reducing shared_buffers to 4GB. Without as many reads, your writes should be much less disruptive. You'll need to restart PG to adopt that change. But I encourage you to keep iostat running in a terminal window so you can watch it for a while. It's very revealing. -- Shaun Thomas OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604 312-444-8534 stho...@optionshouse.com ______________________________________________ See http://www.peak6.com/email_disclaimer/ for terms and conditions related to this email -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
