Re: The results of my PostgreSQL/filesystem performance tests

> What it still leaves quite open is just what happens when the OS has
> more than one disk drive or CPU to play with. It's not clear what
> happens in such cases, whether FreeBSD would catch up, or be "left
> further in the dust." The traditional "propaganda" has been that
> there are all sorts of reasons to expect PostgreSQL on FreeBSD to
> run a bit faster than on Linux; it is a bit unexpected for the
> opposite to seem true.

Let me nip this in the butt before people run away with ideas that
aren't correct. When the tests were performed in FreeBSD 5.1 and
Linux, the hard drives were running UDMA. When running 4.8, for some
reason his drives settled in on PIO mode:

ad0s1a: UDMA ICRC error writing fsbn 1458368 of 729184-729215 (ad0s1 bn 1458368; cn 241 tn 12 sn 44) retrying
ad0s1a: UDMA ICRC error writing fsbn 1458368 of 729184-729215 (ad0s1 bn 1458368; cn 241 tn 12 sn 44) retrying
ad0s1a: UDMA ICRC error writing fsbn 1458368 of 729184-729215 (ad0s1 bn 1458368; cn 241 tn 12 sn 44) retrying
ad0s1a: UDMA ICRC error writing fsbn 1458368 of 729184-729215 (ad0s1 bn 1458368; cn 241 tn 12 sn 44) falling back to PIO mode

The benchmarks were hardly conclusive as UDMA runs vastly faster than
PIO. Until we hear back as to whether cables were jarred loose
between the tests or hearing if something else changed, I'd hardly
consider these conclusive tests given PIO/UDMA is apples to oranges in
terms of speed and I fully expect that FreeBSD 4.8 will perform at
least faster than 5.1 (5.x is still being unwound from Giant), but
should out perform Linux as well if industry experience iss any
indicator.

-sc

--
Sean Chittenden