From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id n0GNDl1o007588 for ; Fri, 16 Jan 2009 17:13:47 -0600 Received: from mx2.redhat.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id BF2501BA4E15 for ; Fri, 16 Jan 2009 15:13:38 -0800 (PST) Received: from mx2.redhat.com (mx2.redhat.com [66.187.237.31]) by cuda.sgi.com with ESMTP id OyOiFsWgVSSkJj4z for ; Fri, 16 Jan 2009 15:13:38 -0800 (PST) Message-ID: <49710AA4.3000402@sandeen.net> Date: Fri, 16 Jan 2009 16:31:00 -0600 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: XFS without write barriers - safe on multipath device? References: <8998fba30901161409m37058e10yc25e062fad425710@mail.gmail.com> In-Reply-To: <8998fba30901161409m37058e10yc25e062fad425710@mail.gmail.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Adam Fried-Gintis Cc: xfs@oss.sgi.com Adam Fried-Gintis wrote: > Hi, > I am just curious, if I see the warning that write barrier support is > disabled when mounting an XFS filesystem through md multipath, does XFS have > some OTHER provision for protecting the order of its writes to the > underlying device, or is it unsafe to run with write back caching at that > point? My underlying device is an active/active storage system - combined > with the multipath driver, we are seeing metadata corruption on the > filesystem, and I'm just trying to figure out if this is an invalid > configuration to test or if the storage device is doing something wrong. XFS needs to know that when the storage says a write is complete, that it really is safe on disk. You're ok w/o barriers if either: a) you have no write cache, or b) you know your write cache is guaranteed to hit the disks (UPS?) Also, this only comes into play when the drives lose power and lose their write cache. If that's not happening to you, then your problem is likely not related to barrier issues. When you say active/active; do you have 2 hosts directly accessing the same filesystem on a SAN? -Eric > Thanks! > > --- > Adam Fried-Gintis _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs