From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Greaves Subject: Re: Questions about software RAID Date: Tue, 19 Apr 2005 09:08:40 +0100 Message-ID: <4264BC88.4050209@dgreaves.com> References: <1113853825.1483.34.camel@debian> <426414A5.3020706@dgreaves.com> <1113865936.1483.73.camel@debian> <20050419071514.GB29247@percy.comedia.it> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20050419071514.GB29247@percy.comedia.it> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids 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 > > >>> >4) I guess the partitions itself doesn't have to be formated as the >>> >filesystem is on the RAID-level. Is that correct? >>> compulsory! >> >> >> I meant, the /dev/mdX has to be formatted, not the individual >> partitions. Still right? > > compulsory! if you do anything on the individual components you'll > damage data. > >>> >5) Removing a disk requires that I do a "mdadm -r" on all the >>> partitions >>> >that is involved in a RAID array. I attempt to by a hot-swap capable >>> >controler, so what happens if I just pull out the disk without this >>> >manual removal command? >>> as far as md is concerned the disk disappeared. >>> I _think_ this is just like mdadm -r. >> > i think it will be marked faulty, not removed. yep - you're right, I remember now. You have to mdadm -r remove it and re-add it once you restore the disk. > >> So I could actually just pull out the disk, insert a new one and do a >> "mdadm -a /dev/mdX /dev/sdY"? >> The RAID system won't detect the newly inserted disk itself? > > no, think of it as flexibility. if you want you can build something > using the "hotplug" subsystem. or: no, it would be mighty strange if the raid subsystem just grabbed every new disk it saw... Think of what would happen when I insert my camera's compact flash card and it suddenly gets used as a hot spare I'll leave Luca's last word - although it's also worth re-reading Peter's first words!! David > one last word: > never trust howtos (they should be called howidid), they have the > tendency to apply to the author configuration, not yours. > general documentation is far more accurate.