Re: Re: WAL and commit_delay

On Sun, Feb 18, 2001 at 11:51:50AM -0500, Tom Lane wrote:
> Adriaan Joubert <a(dot)joubert(at)albourne(dot)com> writes:
> > fdatasync() is available on Tru64 and according to the man-page behaves
> > as Tom expects. So it should be a win for us.
>
> Careful ... HPUX's man page also claims that fdatasync does something
> useful, but it doesn't. I'd recommend an experiment. Does today's
> snapshot run any faster for you (without -F) than before?

It's worth noting in documentation that systems that don't have
fdatasync(), or that have the phony implementation, can get the same
benefit by using a raw volume (partition) for the log file. This
applies even on Linux 2.0 and 2.2 without the "raw-i/o" patch. Using
raw volumes would have other performance benefits, even on systems
that do fully support fdatasync, through bypassing the buffer cache.

(The above assumes I understood correctly Vadim's postings about
changes he made to support putting logs on raw volumes.)

Nathan Myers
ncm(at)zembu(dot)com