From mboxrd@z Thu Jan 1 00:00:00 1970 From: Max Waterman Subject: Re: raid1: All my data completely vanished into the void Date: Wed, 28 Dec 2005 16:23:53 +0800 Message-ID: References: <200512280030.51387.mlaks@verizon.net> <87ek3xsoub.fsf@rimspace.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87ek3xsoub.fsf@rimspace.net> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Daniel Pittman wrote: > Sebastian Kuzminsky writes: >> Mitchell Laks wrote: >>> What does doing >>> >>> mdadm -Cv -n2 -l1 /dev/md0 /dev/sda /dev/sdb >>> >>> do to the partition tables??? >>> (And why can I still access the data if I messed up the partitions??? very >>> odd). >>> Can you point me at an explanation of the effects of what I did? >> I'd expect that command to overwrite the partition table with the >> MD metadata, or at least put the partition table at risk of being >> overwritten later. > > Nope: the MD metadata lives at the end of the disk, not the start, so > your partition table would still be there when the filesystem wrote over > the first block of the disk... > > ....and, if the partition table lived through that, I guess the > filesystem doesn't use (or respects) that block itself. ...but, just so as I understand, by using the whole disk (ie /dev/sda and not /dev/sda1, etc), you're telling md to make the whole disk available to your filesystem (or whatever), including the space normally used to store the partition table, and so any partition table that happens to be on the disk(s) is likely to be over-written. right? Max.