On Tue, Jul 30, 2013 at 8:35 AM, German Becker <german.bec...@gmail.com>wrote:
> 256 was set some time when we were testing a differnt issue. I read that > the only drawback is the amunt of time required for recovery, which was > tested and it was like 10 seconds for the 256 segments, and higher values > mean less disk usage. > Anyway all these parameters should affect the throughput to the data > disks, not the WAL, Am I right? > > checkpoint_completion_target is to help with "checkpoint smoothing", to reduce the spike in disk I/O when shared_buffers are written out. Depesz has a good article about that: http://www.depesz.com/2010/11/03/checkpoint_completion_target/ Do your graphs show any correlation between number of WAL segments getting recycled, and disk I/O spikes? Are you logging checkpoints? If so, you could use the checkpoint times to compare against your I/O graphs. I am by no means an expert here, I'm just throwing out ideas (which might already have been suggested).
