From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Tue, 19 Sep 2006 00:03:02 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id k8J72maG019244 for ; Tue, 19 Sep 2006 00:02:50 -0700 Message-ID: <450F9617.2020603@sgi.com> Date: Tue, 19 Sep 2006 17:02:47 +1000 From: Timothy Shimmin MIME-Version: 1.0 Subject: Re: swidth with mdadm and RAID6 References: <450F1A1F.1020204@agami.com> <450F7C1E.5020300@sgi.com> <450F91D4.1030606@agami.com> In-Reply-To: <450F91D4.1030606@agami.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Shailendra Tripathi Cc: cousins@umit.maine.edu, "\"xfs@oss.sgi.com\" " Shailendra Tripathi wrote: > > Hi Tim, > >> I'm not that au fait with RAID and md, but looking at what you wrote, >> Shailendra, and the md code, instead of your suggestions >> (what I think are your suggestions:) of: >> >> (1) subtracting parity from md.raid_disk (instead of md.nr_disks) >> where we work out parity by switching on md.level >> or >> (2) using directly: (md.nr_disks - md.spares); >> >> that instead we could use: >> (3) using directly: md.active_disks >> >> i.e. >> *swidth = *sunit * md.active_disks; >> I presume that active is the working non spares and non-parity. >> >> Does that make sense? > I agree with you that for operational raid since there would not > be any faulty disks, active disks should the number of disks. However, I > am just concerned that active disks tracks live disks (not failed > disks). If we ever used these commands when the system has faulty drive, > the information returned wouldn't be correct. Though, from XFS > perspective, I can't think of where it can happen. > I would still say that lets rely more on raid_disks to be more > conservative, just my choice. I see your point. I can just change md_get_subvol_stripe(): s/nr_disks/raid_disks/ I just liked the idea of removing the switch statement which could potentially get out of date in the future. Too bad :) --Tim