From owner-freebsd-performance@FreeBSD.ORG  Tue Jun 27 07:41:53 2006
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Date: Tue, 27 Jun 2006 00:41:46 -0700 (PDT)
From: "R. B. Riddick" <arne_woerner@yahoo.com>
To: leo huang <leo.huang.list@gmail.com>
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Cc: freebsd-performance@freebsd.org
Subject: Re: Is the fsync() fake on FreeBSD6.1?
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On Tuesday, 27 June 2006 at 10:18:47 +0800, leo huang wrote:
> And how I can confirm this?
> 
You could do this test:
1. write some data with dd if=/dev/zero of=/tmp/a bs=1m count=100
2. then fsync /tmp/a
3. then listen to the hard disc
4. repeat it until u r sure, if the hard disc reacts on the fsync command...
:-)

I do not know, if it is possible to turn off the write cache of a SCSI disc...

On the freebsd-geom@ list was something about a new feature (the BIO_FLUSH
request), that can flush the write caches of hard discs. But it just works for
ata and amr discs currently... See:
http://docs.freebsd.org/cgi/getmsg.cgi?fetch=3624+0+archive/2006/freebsd-geom/20060625.freebsd-geom

-Arne


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