On Wed, 2007-07-11 at 23:10 -0400, Greg Smith wrote: > All this talk of WAL writing lately has me wondering something I haven't > spent enough time looking at the source to figure out myself this > week...any good rules of thumb out there for estimating WAL volume? I'm > used to just measuring it via benchmarking but it strikes me a formula > would be nice to have for pre-planning. > > For example, if I have a table where a typical row is X bytes wide, and > I'm updating Y of those per second, what's the expected write rate of WAL > volume? Some % of those writes are going to be full pages; what's > typical? How much does the number and complexity of indexes factor into > things--just add the width of the index in bytes to the size of the > record, or is it worse than that?
I published an analysis of WAL traffic from Greg Stark earlier, based upon xlogdump. http://archives.postgresql.org/pgsql-hackers/2007-03/msg01589.php Other details of WAL volumes are in the code. Further analysis would be welcome, to assist discussions of where to optimize next. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 1: 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
