Tom Lane wrote:
The various testing that's been reported so far is all for
Linux and thus doesn't directly address the question of whether other
kernels will have similar performance properties.
Survey of some popular platforms:
Linux: don't want O_DIRECT by default for reliability reasons, and
there's no clear performance win in the default config with small
wal_buffers
Solaris: O_DIRECT doesn't work, there's another API support has never
been added for; see
http://blogs.sun.com/jkshah/entry/postgresql_wal_sync_method_and
Windows: Small reported gains for O_DIRECT, i.e 10% at
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01615.php
FreeBSD: It probably works there, but I've never seen good performance
tests of it on this platform.
Mac OS X: Like Solaris, there's a similar mechanism but it's not
O_DIRECT; see
http://stackoverflow.com/questions/2299402/how-does-one-do-raw-io-on-mac-os-x-ie-equivalent-to-linuxs-o-direct-flag
for notes about the F_NOCACHE feature used. Same basic situation as
Solaris; there's an API, but PostgreSQL doesn't use it yet.
So my guess is that some small percentage of Windows users might notice
a change here, and some testing on FreeBSD would be useful too. That's
about it for platforms that I think anybody needs to worry about.
--
Greg Smith 2ndQuadrant US g...@2ndquadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
