Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934303AbZIDVaE (ORCPT ); Fri, 4 Sep 2009 17:30:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934116AbZIDVaB (ORCPT ); Fri, 4 Sep 2009 17:30:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38003 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932751AbZIDVaA (ORCPT ); Fri, 4 Sep 2009 17:30:00 -0400 Message-ID: <4AA186B0.5090905@redhat.com> Date: Fri, 04 Sep 2009 17:29:20 -0400 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Lightning/1.0pre Thunderbird/3.0b3 MIME-Version: 1.0 To: Mark Lord CC: Krzysztof Halasa , Christoph Hellwig , Michael Tokarev , david@lang.hm, Pavel Machek , Theodore Tso , NeilBrown , Rob Landley , Florian Weimer , Goswin von Brederlow , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, corbet@lwn.net Subject: Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage References: <20090828064449.GA27528@elf.ucw.cz> <20090828120854.GA8153@mit.edu> <20090830075135.GA1874@ucw.cz> <4A9A88B6.9050902@redhat.com> <4A9A9034.8000703@msgid.tls.msk.ru> <20090830163513.GA25899@infradead.org> <4A9BCCEF.7010402@redhat.com> <20090831131626.GA17325@infradead.org> <4A9BCDFE.50008@rtr.ca> <20090831132139.GA5425@infradead.org> <4A9F230F.40707@redhat.com> <4A9FA5F2.9090704@redhat.com> <4A9FC9B3.1080809@redhat.com> <4A9FCF6B.1080704@redhat.com> <4AA184D7.1010502@rtr.ca> In-Reply-To: <4AA184D7.1010502@rtr.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1191 Lines: 34 On 09/04/2009 05:21 PM, Mark Lord wrote: > Ric Wheeler wrote: > .. >> You must disable the write cache on these commodity drives *if* the >> MD RAID level does not support barriers properly. > .. > > Rather than further trying to cripple Linux on the notebook, > (it's bad enough already).. People using MD on notebooks (not sure there are that many using RAID5 MD) could leave their write cache enabled. > > How about instead, *fixing* the MD layer to properly support barriers? > That would be far more useful, productive, and better for end-users. > > Cheers Fixing MD would be great - not sure that it would end up still faster (look at md1 devices with working barriers with compared to md1 with write cache disabled). In the mean time, if you are using MD to make your data more reliable, I would still strongly urge you to disable the write cache when you see "barriers disabled" messages spit out in /var/log/messages :-) ric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/