From mboxrd@z Thu Jan 1 00:00:00 1970 From: den RDC Subject: RAID 5 - All superblocks gone due to MBR/GPT mishap - how do i figure out chunk size? Date: Thu, 16 May 2013 21:24:12 +0200 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hello Due to a nasty (human) error, 4 2tb disks in raid5 have lost their 1st megabyte of data ( including superblock ). In an attempt to get the array to a state usable enough to at least attempt data recovery, I have been trying to re-enable the array using various chunk size and partition start offsets, but i cant seem to get it anywhere near a consistent state ( recovery tools only return files or pieces of files smaller then the chunk size, indicating alignment/chunk size inconsistencies ). The data I do have is : - the order of the disks - the pretty solid assumption that all data, even parity should be fine for most of the disk except the very beginning. - the exact size of the MD device before it got corrupted. Is there any way, however adventurous, to glean the missing data ( chunk size, chunk alignment/offset ) from analysis of the existing data ? Kind regards den_RDC