Re: Bgwriter behavior

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: John Hansen <john(at)geeknet(dot)com(dot)au>,Simon Riggs <simon(at)2ndquadrant(dot)com>,Gavin Sherry <swm(at)linuxworld(dot)com(dot)au>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Bgwriter behavior
Date: 2004-12-28 18:22:06
Message-ID: 200412281822.iBSIM6e03624@candle.pha.pa.us
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Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > John Hansen wrote:
> >> On another note, how do you know for sure, that your drive does not lie
> >> about fsync?
>
> > I just tried and got 115tps with fsync off vs 100 with fsync on, so
> > fsync is certainly doing something.
>
> [ raised eyebrow... ] Something is wrong with that. I'd expect a
> *much* higher difference. It's difficult to credit a tps rate higher
> than your disk's RPM rating with fsync on, but most modern CPUs can do
> a lot better than that with fsync off. If you have a 7200 RPM drive
> then I'd believe the 100 figure, but not the other ...

I think it is a 10k RPM drive, Seagate Cheteetah ST336607LW.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

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