Re: Advice configuring ServeRAID 8k for performance

Greg Smith wrote:
> > 2) Should I configure the ext3 file system with noatime and/or
> > data=writeback or data=ordered? My controller has a battery, the
> > logical drive has write cache enabled (write-back), and the physical
> > devices have write cache disabled (write-through).
>
> data=ordered is the ext3 default and usually a reasonable choice. Using
> writeback instead can be dangerous, I wouldn't advise starting there.
> noatime is certainly a good thing, but the speedup is pretty minor if
> you have a battery-backed write cache.

We recomment 'data=writeback' for ext3 in our docs:

http://www.postgresql.org/docs/9.0/static/wal-intro.html

Tip: Because WAL restores database file contents after a crash,
journaled file systems are not necessary for reliable storage of the
data files or WAL files. In fact, journaling overhead can reduce
performance, especially if journaling causes file system data to be
flushed to disk. Fortunately, data flushing during journaling can often
be disabled with a file system mount option, e.g. data=writeback on a
Linux ext3 file system. Journaled file systems do improve boot speed
after a crash.

Should this be changed?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +