From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C9C1C433EF for ; Tue, 16 Nov 2021 16:41:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 589F1617E4 for ; Tue, 16 Nov 2021 16:41:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235674AbhKPQoJ (ORCPT ); Tue, 16 Nov 2021 11:44:09 -0500 Received: from smtp.hosts.co.uk ([85.233.160.19]:38905 "EHLO smtp.hosts.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233238AbhKPQoJ (ORCPT ); Tue, 16 Nov 2021 11:44:09 -0500 Received: from host81-132-12-162.range81-132.btcentralplus.com ([81.132.12.162] helo=[192.168.1.218]) by smtp.hosts.co.uk with esmtpa (Exim) (envelope-from ) id 1mn1WB-0007CH-3U; Tue, 16 Nov 2021 16:41:11 +0000 Subject: Re: [PATCH] md: fix update super 1.0 on rdev size change To: Markus Hochholdinger , Xiao Ni Cc: Song Liu , linux-raid References: <20211112142822.813606-1-markus@hochholdinger.net> <181899007.qP1mJhO4kW@enterprise> <3122218.nCYcmegLye@enterprise> From: Wols Lists Message-ID: <79efe789-e018-686c-e6ac-554ad99c4866@youngman.org.uk> Date: Tue, 16 Nov 2021 16:41:10 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <3122218.nCYcmegLye@enterprise> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On 16/11/2021 09:28, Markus Hochholdinger wrote: > By using metadata 1.0, the super block is at the end on the logical volumes > and you can easily do a snpashot of the logical volumes and mount the snapshot > for backups without calculating or guessing an offset. Dunno whether now is the time, but if you're moving superblocks, can we think about (a) moving superblocks to convert between 1.0, 1.1 and 1.2, and (b) possibly leaving backup copies lying around. As I say, now might not to be the time to do it, but if you're thinking about it, an easy way to do it might just hit you in the face, and you won't leave any landmines if someone comes along later to do it. (As maintainer of the raid wiki, backup superblocks assisting raid recovery might be a VERY useful tool !!!) Cheers, Wol