From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tregaron Bayly Subject: Specifying a data offset? Date: Wed, 08 May 2013 14:17:54 -0600 Message-ID: <1368044274.3368.364.camel@148> Reply-To: tbayly@bluehost.com Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid List-Id: linux-raid.ids We have lots of mirrors all over our network and over time this means arrays created by different versions of mdadm. In turn this means that we have all sorts of data offsets, including a 2.3.5 mdadm version that offset the data 262,144 sectors. I can't fathom why I need my data to start 128M from the beginning of the disk, but whatever. Inevitably an admin decided that doing a --create over the top of an existing array was a good and necessary thing and when finished we couldn't find the filesystem. Bringing it back online was simply a case of finding the correct offset, locating an mdadm version that would specify it properly and doing another create. Through the whole exercise I found myself wondering why there isn't a command line argument to specify the data offset if something other than the default is desired. I think that implementing the argument and reading the value in init_super wouldn't be terribly difficult so I must be missing an obvious reason. Can someone explain to me why this feature isn't desirable? Thanks, Tregaron