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Date: Tue, 13 Feb 2007 09:47:02 -0500
From: Theodore Tso <tytso@mit.edu>
To: "Martin A. Fink" <fink@mpe.mpg.de>
Cc: Alan <alan@lxorguk.ukuu.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: SATA-performance: Linux vs. FreeBSD
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On Tue, Feb 13, 2007 at 01:32:34PM +0100, Martin A. Fink wrote:
> > Does the FreeBSD fsync sync to media ? Also what controller is being used
> > here, and do you have EHCI USB support running ?
>
> Manual of FreeBSD fsync says it syncs to media.

That didn't answer the question.  With SATA in particular, just
because you flush it to the *disk*, doesn't mean that you've flushed
it to the *media*, unless the OS is explicitly giving an command to
the disk to do so.  If you haven't done any tests where you sync a
huge amount of data on FreeBSD, and then immediate manually kick the
power plug out of the wall, and then checking to make sure all of the
data actually did make it to the media, I wouldn't necessary assume
that it has.  Given that it sounds like you really care about this,
I'd suggest that you explicitly testing this before making
assumptions.

							- Ted
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