On Wed, Sep 14, 2011 at 04:00:54PM +1000, Toby Corkindale wrote:
ZFS (defaults): natty: 171 oneiric: 996
did you tune the fs for database use? e.g. make a separate zfs for ~postgres and give it an 8K block size. apparently it's also a good idea to reduce/limit the size of the ARC (ZFS's equivalent to Linux's disk buffering & caching) because, by default, it will use up all available unused memory less 1GB. The db server will will some or all of that RAM, and db servers often have their own built-in app specific caching too (mysql certainly does). i haven't really looked into tuning ZFS yet, but i have run across some web pages with useful info. http://www.solarisinternals.com/wiki/index.php/ZFS_for_Databases#PostgreSQL_... http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Tuning_... also, ZFS has built in support for write intent logging (ZIL) and caching (L2ARC) on a separate block device (i.e. disk or partition). e.g on an SSD or other fast disk. a couple of GB of ZIL will really speed up random write performance (similar to having a battery-backed or SSD non-volatile write cache on a raid controller) and a separate cache will speed up reads. no idea about your questions. i really don't know ZFS well enough yet to even guess. craig -- craig sanders <cas@taz.net.au> BOFH excuse #277: Your Flux Capacitor has gone bad.