Re: win32 performance - fsync question

On Thu, 17 Feb 2005, Tom Lane wrote:

> Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:
>>> WinXP  fsync = true     20-28 tps
>>> WinXP  fsync = false      600 tps
>>> Linux  fsync = true       800 tps
>>> Linux  fsync = false      980 tps
>
>> Wow, that's terrible on Windows.  If there's a solution, it'd be nice to
>> backport it...
>
> Actually, the number that's way out of line there is the Linux w/fsync
> one.  I infer that he's got disk write cache enabled and therefore the
> transactions aren't really being synced to disk at all.
>
> Any claimed TPS rate exceeding your disk drive's rotation rate is a
> red flag.

Write cache is enabled under Linux by default all the time I make deal
with it (since 1993).

It doesn't interfere with fsync(), as linux kernel uses cache flush for
fsync.

I have 2.6.10 kernel running *without* any additional patches, and without
any specific hdparm settings.

fsync() really works fine as I switch off my notebook everyday 2-3 times,
and never had any data loss :)

Related staff from dmesg is

hda: cache flushes supported


Regards,
E.R.
_________________________________________________________________________
Evgeny Rodichev                          Sternberg Astronomical Institute
email: er@sai.msu.su                              Moscow State University
Phone: 007 (095) 939 2383
Fax:   007 (095) 932 8841                       http://www.sai.msu.su/~er