From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: [Fwd: Re: Missing superblock on one of the raid devices on raid 0 with 1.2 metadata] Date: Fri, 15 Mar 2013 12:52:50 -0400 Message-ID: <514351E2.5030408@turmel.org> References: <1363335578.29317.0.camel@hanna64.taxback.ess.ie> <1363335845.18187.10.camel@gandalf.taxback.ess.ie> <51434C5B.9080007@mpstor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51434C5B.9080007@mpstor.com> Sender: linux-raid-owner@vger.kernel.org To: Benjamin ESTRABAUD Cc: Ivan Yordanov , Nikolay Kichukov , linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi Ivan, On 03/15/2013 12:29 PM, Benjamin ESTRABAUD wrote: [trim /] > The fact that you have the position of all the other drives from the > array is good. Now we want the last drive's superblock to be written. > Since we know the position of all the drives, and assuming you know the > *exact* arguments passed to mdadm when you first created your raid0 > (correct metadata version, chunk size, etc. (most can be found in the > existing superblocks), you could call "mdadm --create " with the same > version of mdadm and MD used when creating the array initially, the same > options and arguments, and *very important* the drives in the same > order, which I believe to be: /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 > (according to the info above). > > This will create a new array, but since you are recreating the same > *exact* array, the existing data should be there and available untouched. This is all correct, and is the correct next step. > However, as a word of warning, many things can go wrong this this > command: If you were to recreate the array slightly differently and > start overwriting your array you would destroy the data on it. The fact > that it is a RAID0 is good since creating a new array won't start a > resync that could be fatal should you have made a mistake providing the > arguments for the recreation. So the above should be generally safe, > provided you keep a copy of the information you gave us above and match > the "create" arguments perfectly. You can check your work by re-issuing the "mdadm -E" commands after re-creating the array. The data offset and chunk size must match the originals. If they do, then you can mount the filesystem. Phil