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

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Message-ID: <480CD9CD.70607@emc.com>
Date:	Mon, 21 Apr 2008 14:15:41 -0400
From:	Ric Wheeler <ric@....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)



Andi Kleen wrote:
> On Mon, Apr 21, 2008 at 12:42:42AM +0100, Jamie Lokier wrote:
>> Andi Kleen wrote:
>>> [LVM] always disables barriers if you don't apply a so far unmerged
>>> patch that enables them in some special circumstances (only single
>>> backing device)
>> (I continue to be surprised at the un-safety of Linux fsync)
> 
> Note barrier less does not necessarily always mean unsafe fsync,
> it just often means that.
> 
> Also surprisingly lot more syncs or write cache off tend to lower the MTBF 
> of your disk significantly, so "unsafer" fsync might actually be more safe
> for your unbackuped data.
> 

Hi Andi,

Where did you get this data?

I have never heard that using more barrier operations lowers the reliability or 
the MTBF of a drive and I look at a fairly huge population when doing this ;-)

ric



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