Thread: Direct I/O and postgresql version
Hi All, I have one question. Which of the recent versions of postgresql support direct I/O? Thanks, Dipali Pal
Pal, Dipali (UMKC-Student) wrote: > Hi All, > > I have one question. > Which of the recent versions of postgresql support direct I/O? > that would be, none.
On Tue, 19 May 2009, Pal, Dipali (UMKC-Student) wrote: > Which of the recent versions of postgresql support direct I/O? As of 8.1 PostgreSQL does direct I/O for writes to the WAL if you've configured wal_sync_method={open_datasync,open_sync} on supported platforms. I know Linux works but Solaris doesn't. See http://www.postgresql.org/docs/current/static/runtime-config-wal.html#GUC-WAL-SYNC-METHOD and http://www.postgresql.org/docs/current/static/wal-configuration.html for more details. The usual workaround for the Solaris problem is to split the WAL pg_xlog directory onto another filesystem and change its mounting options, see http://blogs.sun.com/jkshah/entry/postgresql_wal_sync_method_and for more about that. There is no option to do direct writes for the main database I/O because the database usually performs better if you rely on the filesystem cache. You can certainly find situations where sync writes end up working out better, but they're not common. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD