From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: RAID, ext4, barriers Date: Mon, 23 Nov 2009 11:29:59 -0500 Message-ID: <4B0AB887.3040801@redhat.com> References: <4AF6F975.8030903@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4AF6F975.8030903@gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Andrew Dunn Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 11/08/2009 12:01 PM, Andrew Dunn wrote: > I noticed this in my dmesg: > > [ 7089.116953] JBD: barrier-based sync failed on md0:8 - disabling barriers > [ 9296.850098] JBD: barrier-based sync failed on md1:8 - disabling barriers > > I was wondering if this is a problem. I saw some links where people were > listing this as a bug report for ext[2,3,4] partitions. I don't know if > it will be a problem for me, any experience? > > Hi Andrew, If you are worried about losing power on this RAID set, you need to make sure that the write cache on the individual drives is disabled. Without barriers, you can bet that the file system will lose data after a power hit. Note that not all MD raid levels support barriers, although I think that Neil posted some patches that tried to close that gap, Ric