From: Eric Sandeen Subject: Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem checker) Date: Mon, 21 Apr 2008 13:25:01 -0500 Message-ID: <480CDBFD.30009@redhat.com> References: <20080419012952.GE25797@mit.edu> <20080419185603.GA30449@mit.edu> <480A42F6.2030005@redhat.com> <20080419220432.GB30449@mit.edu> <87iqyc85q7.fsf@basil.nowhere.org> <20080420234241.GB23292@shareable.org> <20080421080111.GD14446@one.firstfloor.org> <480CD9CD.70607@emc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Andi Kleen , Theodore Tso , Alexey Zaytsev , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, Rik van Riel To: ric@emc.com Return-path: In-Reply-To: <480CD9CD.70607@emc.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Ric Wheeler wrote: > > 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, what about the other part - turning write cache off? I've also heard it suggested that this might hurt drive lifespan, and it sorta makes sense, I assume it keeps the head working harder... -Eric