From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id EC4637F5A for ; Thu, 26 Sep 2013 03:44:07 -0500 (CDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay2.corp.sgi.com (Postfix) with ESMTP id D7323304059 for ; Thu, 26 Sep 2013 01:44:07 -0700 (PDT) Received: from greer.hardwarefreak.com (mo-65-41-216-221.sta.embarqhsd.net [65.41.216.221]) by cuda.sgi.com with ESMTP id fSBR8qfgGhHDexaX for ; Thu, 26 Sep 2013 01:44:07 -0700 (PDT) Message-ID: <5243F3DE.3050900@hardwarefreak.com> Date: Thu, 26 Sep 2013 03:44:14 -0500 From: Stan Hoeppner MIME-Version: 1.0 Subject: Re: xfs hardware RAID alignment over linear lvm References: <52435327.9080607@hardwarefreak.com> <2F959FD9-EF28-4495-9D0B-59B93D89C820@colorremedies.com> <20130925215713.GH26872@dastard> In-Reply-To: <20130925215713.GH26872@dastard> Reply-To: stan@hardwarefreak.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 Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: Chris Murphy , "xfs@oss.sgi.com" On 9/25/2013 4:57 PM, Dave Chinner wrote: ... > Linear concatentation looks like this: > > offset volume array > 0 +-D1-+-D2-+.....+-Dn-+ 0 # first sw > ..... > X-sw +-D1-+-D2-+.....+-Dn-+ 0 > X +-E1-+-E2-+.....+-En-+ 1 # first sw > ..... > 2X-sw +-E1-+-E2-+.....+-En-+ 1 > 2X +-F1-+-F2-+.....+-Fn-+ 2 # first sw > ..... > 3X-sw +-F1-+-F2-+.....+-Fn-+ 2 > > Where: > D1...Dn are the disks in the first array > E1...En are the disks in the second array > F1...Fn are the disks in the third array > X is the size of the each array > sw = su * number of data disks in array > > As you can see, all the volumes are arranged in a single column - > identical to a larger single array of the same size. Hence the > exposed alignment of a single array is what the filesystem should be > aligned to, as that is how the linear concat behaves. > > You also might note here that if you want the second and subsequent > arrays to be correctly aligned to the initial array in the linear > concat (and you do want that), the arrays must be sized to be an > exact multiple of the stripe width. On a similar note, if I do a concat like this I specify agsize/agcount during mkfs.xfs so no AGs straddle array boundaries. I do this to keep per AG throughput consistent, among other concerns. This may or may not be of benefit to the OP. mkfs.xfs using defaults is not aware of the array boundaries within the concat, so it may well create AGs across array boundaries. -- Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs