On Fri, 13 Aug 2010 14:17:17 +0800 Craig Ringer <craig@xxxxxxxxxxxxxxxxxxxxx> wrote: > On 13/08/10 08:38, Tatsuo Ishii wrote: > >> It's slower than smaller numbers, and if you actually dirty a > >> significant portion of it you can have a checkpoint that takes > >> hours to sync, completely trashing system responsiveness for a > >> good portion of it. > > > > So how much is the reasonal upper limit of shared_buffers at this > > point? If it's obvious, should we disable or warn to use more > > than that number? > > Trouble is, there won't be a "reasonable upper limit" ... because > it depends so much on the ratio of memory to I/O throughput, the > system's writeback aggressiveness, etc etc etc. > > Personally I've had two Pg machines where one seems to suffer with > shared_buffers > 250MB out of 4GB and the other, which has 8GB of > RAM, wants shared_buffers to be around 4GB! The main difference: > disk subsystems. What about the ratio of R/W? If it is a mostly read system is the memory/IO throughput still a limiting factor for increasing shared_buffers? -- Ivan Sergio Borgonovo http://www.webthatworks.it -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
