From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: Questions about software RAID Date: Tue, 19 Apr 2005 16:18:34 +0400 Message-ID: <4264F71A.9070103@tls.msk.ru> References: <1113853825.1483.34.camel@debian> <426414A5.3020706@dgreaves.com> <1113865936.1483.73.camel@debian> <20050419071514.GB29247@percy.comedia.it> <4264BC88.4050209@dgreaves.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4264BC88.4050209@dgreaves.com> Sender: linux-raid-owner@vger.kernel.org To: David Greaves Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids David Greaves wrote: > Luca Berra wrote: > >> many people find it easier to understand if raid partitions are set to >> 0XFD. kernel autodetection is broken and should not be relied upon. > > Could you clarify what is broken? > I understood that it was simplistic (ie if you have a raid0 built over a > raid5 > or something exotic then it may have problems) but essentially worked. > Could it be : > * broken for complex raid on raid > * broken for root devices > * fine for 'simple', non-root devices It works when everything works. If something does not work (your disk died, you moved disks, or esp. you added another disk from another machine wich was also a part of (another) raid array), every bad thing can happen, from just inability to assemble the array at all, to using the wrong disks/partitions, and to assembling the wrong array (the one from another machine). If it's your root device you're trying to assemble, recovery involves booting from a rescue CD and cleaning stuff up, which can be problematic at times. /mjt