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 B77217F4E for ; Wed, 25 Sep 2013 16:48:07 -0500 (CDT) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay2.corp.sgi.com (Postfix) with ESMTP id A4280304043 for ; Wed, 25 Sep 2013 14:48:07 -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 39MHRs0RFGwBLuWc for ; Wed, 25 Sep 2013 14:48:06 -0700 (PDT) Message-ID: <52435A1B.8040207@hardwarefreak.com> Date: Wed, 25 Sep 2013 16:48:11 -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> In-Reply-To: <2F959FD9-EF28-4495-9D0B-59B93D89C820@colorremedies.com> 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: Chris Murphy Cc: "xfs@oss.sgi.com" On 9/25/2013 4:34 PM, Chris Murphy wrote: > > On Sep 25, 2013, at 3:18 PM, Stan Hoeppner wrote: > >> On 9/25/2013 7:56 AM, Stewart Webb wrote: >>> Hi All, >> >> Hi Stewart, >> >>> I am trying to do the following: >>> 3 x Hardware RAID Cards each with a raid 6 volume of 12 disks presented to >>> the OS >>> all raid units have a "stripe size" of 512 KB >> >> Just for future reference so you're using correct terminology, a value >> of 512KB is surely your XFS su value, also called a "strip" in LSI >> terminology, or a "chunk" in Linux software md/RAID terminology. This >> is the amount of data written to each data spindle (excluding parity) in >> the array. >> >> "Stripe size" is a synonym of XFS sw, which is su * #disks. This is the >> amount of data written across the full RAID stripe (excluding parity). >> >>> so given the info on the xfs.org wiki - I sould give each filesystem a >>> sunit of 512 KB and a swidth of 10 (because RAID 6 has 2 parity disks) >> >> Partially correct. If you format each /dev/[device] presented by the >> RAID controller with an XFS filesystem, 3 filesystems total, then your >> values above are correct. EXCEPT you must use the su/sw parameters in >> mkfs.xfs if using BYTE values. See mkfs.xfs(8) Small correction: su is a byte value. sw is an integer representing the number of data spindles. >>> all well and good >>> >>> But - I would like to use Linear LVM to bring all 3 cards into 1 logical >>> volume - >>> here is where my question crops up: >>> Does this effect how I need to align the filesystem? >> >> In the case of a concatenation, which is what LVM linear is, you should >> use an XFS alignment identical to that for a single array as above. > > So keeping the example, 3 arrays x 10 data disks, would this be su=512k and sw=30? No. In this configuration, as far as XFS is concerned LVM doesn't exist in the stack because it doesn't change the RAID geometry, so you ignore it. -- Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs