Re: win32 performance - fsync question

On Thu, 17 Feb 2005, Tom Lane wrote:

> Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)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
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