> One of the most common causes I've seen for this is linux's vm.*dirty* settings to get in the way. Like so many linux kernel "optimizations" this one looks good on paper but gives at best middling improvements with occasional io storms that block everything else. On big mem machines doing a lot of writing IO I just set these to 0. Also tend to turn off swap as well as it's known to get in the way as well. > > settings for /etc/sysctl.conf > vm.dirty_background_ratio = 0 > vm.dirty_ratio = 0 >
I'll +1 on the "you have to tune your Linux install" advice.
I found the "PostgreSQL 9.0 High Performance" book to be worth its weight in gold. A few days spent with the book and research on mailing lists improved our PostgreSQL performance multiple times over, and responsiveness under load by orders of magnitude.
Yep. That's probably the single most useful performance tuning book anyone working with dbs can own. Even if you don't run postgresql, the hardware tuning and testing section is fantastic.
