From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Greaves Subject: Re: Time to deprecate old RAID formats? Date: Wed, 24 Oct 2007 10:40:48 +0100 Message-ID: <471F1320.1060600@dgreaves.com> References: <18200.49267.763509.924873@stoffel.org> <18200.53593.687483.120827@stoffel.org> <1192810534.1666.68.camel@firewall.xsintricity.com> <471A0C02.4030407@msgid.tls.msk.ru> <18202.5687.672431.295590@stoffel.org> <471A47CC.1070508@msgid.tls.msk.ru> <18205.2688.952701.567195@stoffel.org> <1193186569.10336.30.camel@firewall.xsintricity.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1193186569.10336.30.camel@firewall.xsintricity.com> Sender: linux-raid-owner@vger.kernel.org To: Doug Ledford Cc: John Stoffel , Michael Tokarev , Justin Piszcz , linux-raid@vger.kernel.org List-Id: linux-raid.ids Doug Ledford wrote: > On Mon, 2007-10-22 at 16:39 -0400, John Stoffel wrote: > >> I don't agree completely. I think the superblock location is a key >> issue, because if you have a superblock location which moves depending >> the filesystem or LVM you use to look at the partition (or full disk) >> then you need to be even more careful about how to poke at things. > > This is the heart of the matter. When you consider that each file > system and each volume management stack has a superblock, and they some > store their superblocks at the end of devices and some at the beginning, > and they can be stacked, then it becomes next to impossible to make sure > a stacked setup is never recognized incorrectly under any circumstance. I wonder if we should not really be talking about superblock versions 1.0, 1.1, 1.2 etc but a data format (0.9 vs 1.0) and a location (end,start,offset4k)? This would certainly make things a lot clearer to new users: mdadm --create /dev/md0 --metadata 1.0 --meta-location offset4k mdadm --detail /dev/md0 /dev/md0: Version : 01.0 Metadata-locn : End-of-device Creation Time : Fri Aug 4 23:05:02 2006 Raid Level : raid0 And there you have the deprecation... only two superblock versions and no real changes to code etc David