Write ahead logging

Hi

I am doing some performance testing using postgresql. When measuring the
latency of commit I got some results, which make me doubt, if the logging
data is written to disk in time:

Using a slow disk (5400rpm) I measured about 3-5 ms for a commit. But
average rotational delay is already higher for that disk (5.5ms).
So the question is: has anybody verified, that the log is written to disk
before returning from commit?

System used was:

Linux 2.4.20
filesystem: ext3
postgresql postgresql-7.2

Regards,

    Matthias Meixner

--
Matthias Meixner                       meixner@informatik.tu-darmstadt.de
Technische Universität Darmstadt
Datenbanken und Verteilte Systeme              Telefon (+49) 6151 16 6232
Wilhelminenstraße 7, D-64283 Darmstadt, Germany    Fax (+49) 6151 16 6229