From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from resqmta-ch2-12v.sys.comcast.net ([69.252.207.44]:50262 "EHLO resqmta-ch2-12v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbaKULfJ (ORCPT ); Fri, 21 Nov 2014 06:35:09 -0500 Message-ID: <546F2369.8090605@pobox.com> Date: Fri, 21 Nov 2014 03:35:05 -0800 From: Robert White MIME-Version: 1.0 To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org Subject: Re: BTRFS messes up snapshot LV with origin References: <54699CC7.1050909@swiftspirit.co.za> <546A46A5.8030603@inwind.it> <27BDAC3B-789C-4477-B065-E703CE425F54@colorremedies.com> <546B68F8.6080008@ubuntu.com> <546BA96D.4050805@ubuntu.com> <2A57F99C-80AA-4FD4-AA41-57F02AD4E1A2@colorremedies.com> <546CB531.2060509@ubuntu.com> <20141121042814.GR17395@hungrycats.org> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 11/20/2014 10:22 PM, Duncan wrote: > But while other filesystems might allow un-UUIDs (heh, UUUIDs or U3IDs > =:^), because they're no longer unique, requiring them to be unique just > as the label says cannot be considered a bug. It's simply stricter > enforcement of the rules, which are, after all, plainly stated in the > descriptive name. You take "U"s away, not add them UID = unique ID GUID = globally unique ID UUID = universally unique ID And other file systems have the same issues. XFS, for example uses UUIDs in the same way. It just has a command to re-brand the filesystem's UUID which you apply to the LVM snapshot immediately after taking the snapshot. (problem long-since established and understood since 2009 or so.) I don't know if this approach would work for BRFS with subvolumes. Example Citation :: http://www.miljan.org/main/2009/11/16/lvm-snapshots-and-xfs/ XFS also has the nouuids mount option. btrfs has device= mount option. But any system with unique ids will have this identical issue when block-snapshot support is added underneath. -- Rob.