linux-ext4 - Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem checker)

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Date:	Mon, 21 Apr 2008 19:27:21 +0100
From:	"Ricardo M. Correia" <Ricardo.M.Correia@....COM>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Theodore Tso <tytso@....edu>, Eric Sandeen <sandeen@...hat.com>,
	Alexey Zaytsev <alexey.zaytsev@...il.com>,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Rik van Riel <riel@...riel.com>
Subject: Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem
	checker)

On Seg, 2008-04-21 at 19:40 +0200, Andi Kleen wrote:
> > Is there a reason why this isn't being done other than performance?
> 
> One reason against it is that in many (but not all) setups to guarantee
> reaching the platter you have to disable the write cache, and at least
> for consumer level hard disks disk vendors generally do not recommend
> doing this because it significantly lowers the MTBF of the disk.

I understand that, but if the disk/storage doesn't support flushing the
cache, I would expect fsync() to return EIO or ENOTSUP, I wouldn't
expect it to ignore my request and risk losing data without my
knowledge..

I know fsync() also flushes dirty buffers, but IMHO even if it flushes
the buffers it'd be better to return an error if a full sync wasn't
being done rather than returning success and misleading the application.

Anyway, sorry if this has been discussed before, I should take a look at
the archives..

Thanks,
Ricardo
--

Ricardo Manuel Correia
Lustre Engineering

Sun Microsystems, Inc.
Portugal
Phone +351.214134023 / x58723
Mobile +351.912590825
Email Ricardo.M.Correia@....COM

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