From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id n7KEg3Bj100315 for ; Thu, 20 Aug 2009 09:42:13 -0500 Received: from mx1.redhat.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 218AC3E652F for ; Thu, 20 Aug 2009 07:42:43 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id TIWEYopCj3IGeaBj for ; Thu, 20 Aug 2009 07:42:43 -0700 (PDT) Message-ID: <4A8D60C1.6000809@redhat.com> Date: Thu, 20 Aug 2009 10:42:09 -0400 From: Ric Wheeler MIME-Version: 1.0 Subject: Re: [PATCH, RFC] xfs: batched discard support References: <20090816004705.GA7347@infradead.org> <20090819203916.GA25296@elte.hu> <4A8CA956.2060406@rtr.ca> <4A8D5442.1000302@redhat.com> <4A8D5FDB.7080505@rtr.ca> In-Reply-To: <4A8D5FDB.7080505@rtr.ca> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Mark Lord Cc: Peter Zijlstra , linux-scsi@vger.kernel.org, Neil Brown , linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Christoph Hellwig , IDE/ATA development list , Paul Mackerras , jens.axboe@oracle.com, linux-fsdevel@vger.kernel.org, Ingo Molnar , Linus Torvalds On 08/20/2009 10:38 AM, Mark Lord wrote: > Ric Wheeler wrote: >> >> Note that returning consistent data is critical for devices that are >> used in a RAID group since you will need each RAID block that is used >> to compute the parity to continue to return the same data until you >> overwrite it with new data :-) >> >> If we have a device that does not support this (or is misconfigured >> not to do this), we should not use those devices in an MD group & do >> discard against it... > .. > > Well, that's a bit drastic. But the RAID software should at least > not issue TRIM commands in ignorance of such. If the storage can return different data in a sequence of READ requests of the same sector (with no writes), there is nothing RAID could do. It would see total garbage... > Would it still be okay to do the TRIMs when the entire parity stripe > (across all members) is being discarded? (As opposed to just partial > data there being dropped) This should be safe if the MD bitmaps would prevent us from trying to READ/regenerate parity for that stripe... ric _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs