Excerpts from Tom Lane's message of lun jun 14 23:57:11 -0400 2010: > Scott Carey <sc...@richrelevance.com> writes: > > Great points. There is one other option that is decent for the WAL: > > If splitting out a volume is not acceptable for the OS and WAL -- > > absolutely split those two out into their own partitions. It is most > > important to make sure that WAL and data are not on the same filesystem, > > especially if ext3 is involved. > > Uh, no, WAL really needs to be on its own *spindle*. The whole point > here is to have one disk head sitting on the WAL and not doing anything > else except writing to that file.
However, there's another point here -- probably what Scott is on about: on Linux (at least ext3), an fsync of any file does not limit to flushing that file's blocks -- it flushes *ALL* blocks on *ALL* files in the filesystem. This is particularly problematic if you have pgsql_tmp in the same filesystem and do lots of disk-based sorts. So if you have it in the same spindle but on a different filesystem, at least you'll avoid that extra fsync work, even if you have to live with the extra seeking. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
