Hi Ilya, Thank you for the response. Yes BBU is on the controller; 1024Mb. It is a HP P410i controller, with write caching turned on the controller; off on disk level. 2x 15k SAS SFF for WAL and 12x 10k SAS SFF for DB We have tried longer settings for checkpoint_timeout, but not 1hr; so we will try that as well. We don't at this stage have any graphs, but we will set it up over the next 24hrs at least. Regards, Steve ---------------------------------------- > From: ilya.kosmodemiansky@xxxxxxxxxxxxxxxxxxxxxxxxx > Date: Wed, 18 Mar 2015 12:42:43 +0100 > Subject: Re: Very slow checkpoints > To: steven.jones1201@xxxxxxxxxxx > CC: pgsql-performance@xxxxxxxxxxxxxx > > Hi Steven, > > On Wed, Mar 18, 2015 at 12:21 PM, Steven Jones > <steven.jones1201@xxxxxxxxxxx> wrote: >> - system is HP blade; 128Gb RAM, 2x 8-core, 12x 10k RPM RAID1+0 (database) > > Have you BBU on your controller? And how your controller configured, I > mean cache mode, io mode, disk write cache mode. You have 15K SAS > (which form factor?) under WAL and 10K SAS under database, am I > correct? > >> Full iostat/iotop, configuration, checkpoint stats, etc. are pasted below >> for completeness. Highlights are: >> checkpoint_segments=512 >> shared_buffers=16GB >> checkpoint_timeout=15min >> checkpoint_completion_target=0.1 > > It looks like your checkpoint settings are a bit strange besides of > everything else. If you chose high value for checkpoint_segments, your > aim is to avoid checkpoints by timeout (or vice verse). If you have > checkpoint_segments=512, your checkpoint_timeout should be about > 60min. And anyway - checkpoint_completion_target=0.9 or 0.7 in order > to spread disk load between checkpoints. > > > >> >> sysctl settings for dirty pages >> >> vm.dirty_background_bytes = 0 >> vm.dirty_background_ratio = 5 >> vm.dirty_bytes = 0 >> vm.dirty_expire_centisecs = 3000 >> vm.dirty_ratio = 10 >> vm.dirty_writeback_centisecs = 500 > > Values for this settings are really dependent of RAID (and BBU size). > > And about further problem description: have you any graphical > representation of your % disc utilization? > > Best regards, > Ilya > > -- > Ilya Kosmodemiansky, > > PostgreSQL-Consulting.com > tel. +14084142500 > cell. +4915144336040 > ik@xxxxxxxxxxxxxxxxxxxxxxxxx > > > -- > Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-performance -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
