On Tue, 1 Jul 2003, Michael Mattox wrote: > My understanding is to use as much effect cache as possible, so figure out > how much ram you need for your other applications & OS and then give the > rest to postgres as effective cache. > > What I learned to day is the shared_buffers 25% of RAM guideline.
Note that the best guideline is the one that your testing shows you makes the most sense. If you never access more than a few megs at a time, then there's no need to have 25% of a machine with 1 gig given over to the database's shared buffers, it's better to let the machine cache that for you. If you access hundreds of megs at a time, then 25% of RAM is a good idea. Usually 25% of RAM is about the max that gives good results, but in some corner cases, using more still makes sense. Usually at that point, you've also increased sort_mem up a bit too, but be careful, sort_mem is PER SORT, not per backend or per database cluster, so it can add up very quickly and make the machine run out of RAM. Setting these settings is a lot like playing Jenga (the game with the wooden blocks stacked up where you pull one out and put them on top one at a time.) Everything seems just fine, the machine's getting faster and faster, everybody's loving life, then you crank one up a little too high, cause a swap storm, and the whole thing slows to a crawl. ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly