BTW I have all this data ploted using munin, let me know if you are intrested in looking at the graphs, I send them
On Mon, Jul 29, 2013 at 4:41 PM, German Becker <german.bec...@gmail.com>wrote: > Luis, The disk only has the WAL (pg_xlog ) directory. Brett, Here are the > mount options: > > /dev/sdb1 on /storage/sdb1 type ext3 > (rw,noatime,data=writeback,errors=remount-ro) > > BTW The original fs was ext4, now I am trying with ext3, with the exact > same results. No noticeable changes using diferent journal modes. > > I also tried disabling the journal altogether, which dramatically reduced > the disk usage, but nevertheless there was this latency spikes. > > > On Mon, Jul 29, 2013 at 3:01 PM, Brett Stauner <br...@mightybs.net> wrote: > >> 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 >>>>>> >>>>> >>>>> >>>> >>> >> >
