On Dec 13, 2007 6:06 AM, Ow Mun Heng <Ow.Mun.Heng@xxxxxxx> wrote: > I'm using centos 5 as the OS so, there's no fancy dtrace to look at > which processes is causing my disks to thrash. > > I have 4 disks in the box. (all ide, 7200rpm) > > 1 OS disk [hda] > 2 raided (1) disks [hdb/hdc] > 1 pg_xlog disk (and also used as an alternate tablespace for [hdd] > temp/in-transit files via select, insert into tmp table. delete from tmp > table, insert into footable select * from tmp table) > > Problem now I see from both atop and iostat, the Device: (iostat -dx 10) > > rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util > hda 98.60 14.69 121.98 15.08 1775.02 2908.29 34.17 47.53 551.67 7.29 99.95 > hdb 0.70 4.20 16.48 2.30 304.50 51.95 18.98 0.21 10.94 8.45 15.86 > hdc 0.00 3.40 12.49 2.00 223.78 43.16 18.43 0.07 5.04 4.42 6.40 > hdd 0.00 56.94 0.50 3.70 53.55 485.91 128.57 0.02 5.48 3.95 1.66 > md0 0.00 0.00 29.57 11.89 526.67 95.10 15.00 0.00 0.00 0.00 0.00 > > the number of writes and reads on hda is much greater than expected and I'm not sure who/what is causing it. there are a few things that I can think of that can can cause postgres to cause i/o on a drive other than the data drive: * logging (eliminate this by moving logs temporarily) * swapping (swap is high and changing, other ways) * dumps, copy statement (check cron) * procedures, especially the external ones (perl, etc) that write to disk my seat-of-the-pants guess is that you are looking at swap. of course, a runaway program other than postgres can be the cause merlin ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
