On Wed, Dec 17, 2008 at 2:34 AM, Albe Laurenz <laurenz.albe@xxxxxxxxxx> wrote: > Jaime Casanova wrote: >> we have a some bad queries (developers are working on that), some of >> them run in 17 secs and that is the average but when analyzing logs i >> found that from time to time some of them took upto 3 mins (the same >> query that normally runs in 17secs). >> >> so my question is: how could i look for contention problems? > > A good first step is to identify the bottleneck. > > Frequently, but not always, this is I/O. > Do you see a lot of I/O wait? Are the disks busy? > the disks are an RAID 10 with 4 sata disks of 15000rpm and nop iostat reports avg of 0.12 iowait > I don't know anything about your system, but I once experienced a > similar problem with a 2.6 Linux system where things improved considerably > after changing the I/O-scheduler to "elevator=deadline". > i don't understand I/O-schedulers at all... anyone knows what is the recommended for postgres? -- Atentamente, Jaime Casanova Soporte y capacitación de PostgreSQL Asesoría y desarrollo de sistemas Guayaquil - Ecuador Cel. +59387171157 -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
