On Thu, Oct 3, 2013 at 11:56 PM, Michal TOMA <mt@sicoop.com> wrote:
Now I have: checkpoint_completion_target = 0.9 wal_buffers = 8MB checkpoint_segments = 16 checkpoint_timeout = 20min shared_buffers = 2GB log_checkpoints = on
This is what I can see in the log: 2013-10-03 13:58:56 CEST LOG: checkpoint starting: xlog 2013-10-03 13:59:56 CEST LOG: checkpoint complete: wrote 448 buffers (0.2%); 0 transaction log file(s) added, 9 removed, 18 recycled; write=39.144 s, s, sync=12102.311 s, total=12234.608 s; sync files=667, longest=181.374 s, average=18.144 s 2013-10-03 22:30:25 CEST LOG: checkpoint starting: xlog time
From your logs, it seems that the writes are spread all over the (fairly large) database. Is that correct? What is the database size? What is the size of the working data set (i.e. the set of rows that are in use)?
I heard of people having good results with setting a low value for shared_buffers (like 128MB) in a high write activity scenarios. Setting it that low would mean that checkpoints would have 16 times less to do.