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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 (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
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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