terrible performance in 6.1beta4

[usleepless at gmail.com]

Bill,

> > Actually I seem to recall that on Linux with default settings fsync()
> > lies and does not actually sync data before returning, so maybe it's
> > worth turning off on FreeBSD too if you're comfortable with the
> > implications of this.
>
> If you have fsync off and the system crashes, your PostgreSQL database
> will probably be corrupt beyond repair.

that is not true. that is not "probable", at least, it never happened
to me. and i encountered some panics over the last months ( i have
been patching multimedia/pvr250 to support 500s ).

in fact, PostgreSQL never corrupted on me in 5 years ( i used to use
to mysql, which seemed to corrupt by looking at it ). however, i am
not in the large number of transactions-business. there is a sustained
number of updates though, at least once every 2 minutes.

> I believe the official word from the PostgreSQL folks is that fsync is
> safe to turn off if you've got battery-backed cache on your disk
> controllers.  Many high-end SCSI controllers have this as an option.

interesting, i didn't know.

> Alternatively, if you're just putting the database on for the first
> time, you can temporarily turn fsync off while you're uploading the
> data.  If the system crashes during this, just delete and recreate
> the database and try again.

my suggestion to turn fsync of was geared towards this particular
problem, although i did not explicitly state that.

it is a good thing you are pointing out potential problems.

> It's not generally a good idea to run in production with fsync off,
> however, unless you have a battery on your controller.

While you might be very right, my server only has an UPS, and i am
comfortable with that given the stability of FBSD.

regards,

usleep

>
> --
> Bill Moran
> Potential Technologies
> http://www.potentialtech.com
>