Okay, so it's not happening at the same time of day or anything. What are your mount options for the WAL disk?
On Mon, Jul 29, 2013 at 12:58 PM, German Becker <german.bec...@gmail.com>wrote: > > Brett, > > Yes I'm not impying it is postgres related, perhaps is even a normal thing > of ext3 /ext4 filesystem, but, this behavioiur is only notable when using > postgres and in particular the wal files, as it is very hard disk > intensive, soy maybe somenone has seen this befores. The server only task > is the database. It has 4 disks one for the os, one for the wal and the > other 2 for data. All disks show different access times. The WAL disk is > the only one on which the with constant latency, and in certain ocasions it > goes up. > Plus the ocasions are absolutely random. > > On Mon, Jul 29, 2013 at 1:15 PM, Brett Stauner <br...@mightybs.net> wrote: > >> "...like if the disk/filesystem gets slower during one hour or so" >> >> What about a different scheduled task on the system, not necessarily >> Postgres related? >> >> >> On Mon, Jul 29, 2013 at 9:17 AM, German Becker >> <german.bec...@gmail.com>wrote: >> >>> Alvaro, >>> >>> Thanks for your reply. I believe that the only possibility is autovacum >>> activity I will check that. Anyway what puzzles me is that >>> the throughput does not increase like i might expect if there where high >>> VACUUM activity, only the WAIT TIME and thus the UTILIZATION. Is like if >>> the disk/filesystem gets slower during one hour or so... >>> >>> >>> On Fri, Jul 26, 2013 at 5:27 PM, Alvaro Herrera < >>> alvhe...@2ndquadrant.com> wrote: >>> >>>> German Becker escribió: >>>> > Hi list, >>>> > >>>> > I am running Postgres 9.1 on Ubuntu 12.04. I have a dedicated disk for >>>> > pg_xlog, using ext4 filesystem with journaling in writeback mode >>>> > During high load times, the disk usage is arround 40%. The IO write >>>> time is >>>> > constant at about 3ms. On certain occasions roughly once in 15 days, >>>> the >>>> > IO write time goes up to about 10ms. This makes the disk usage go up >>>> to >>>> > almost 100%, probably saturation, and the INSERTS DELETES UPDATES run >>>> > considerable slower than normal.This lasts for about 2 hours and then >>>> the >>>> > latency goes back to 3ms and everything is normal again. >>>> > Has anyone seen this behavior? What could be causing the increase in >>>> > latency? >>>> >>>> Can you correlate these episodes with autovacuum activity? Or perhaps >>>> backups are being taken (maybe a new base backup is taken every 15 >>>> days)? >>>> >>>> -- >>>> Álvaro Herrera http://www.2ndQuadrant.com/ >>>> PostgreSQL Development, 24x7 Support, Training & Services >>>> >>> >>> >> >
