From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-33-i2.italiaonline.it ([212.48.25.204]:59321 "EHLO smtp-33.italiaonline.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751072AbaKYV75 (ORCPT ); Tue, 25 Nov 2014 16:59:57 -0500 Message-ID: <5474FBD9.5070709@inwind.it> Date: Tue, 25 Nov 2014 22:59:53 +0100 From: Goffredo Baroncelli Reply-To: kreijack@inwind.it MIME-Version: 1.0 To: Zygo Blaxell CC: linux-btrfs Subject: Re: BTRFS messes up snapshot LV with origin References: <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> <5470C92E.1070607@inwind.it> <20141123001927.GO17380@hungrycats.org> <5474AF87.6090702@inwind.it> <20141125202948.GP17380@hungrycats.org> In-Reply-To: <20141125202948.GP17380@hungrycats.org> Content-Type: text/plain; charset=windows-1252 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 11/25/2014 09:29 PM, Zygo Blaxell wrote: > On Tue, Nov 25, 2014 at 05:34:15PM +0100, Goffredo Baroncelli wrote: >> On 11/23/2014 01:19 AM, Zygo Blaxell wrote: >> [...] >>> md-raid works as long as you specify the devices, and because it's always >>> the lowest layer it can ignore LVs (snapshot or otherwise). It's also >>> not a particularly common use case, while making an LV snapshot of a >>> filesystem is a typical use case. >> >> I fully agree; but you still consider a *multi-device* btrfs over lvm... >> This is like a dm over lvm... which doesn't make sense at all (as you >> already wrote) > > It makes sense for btrfs because btrfs can productively use LVs on > different PVs (e.g. btrfs-raid1 on two LVs, one on each PV). LVM is > the bottom layer because not everything in the world is btrfs--things > like ephemeral /tmp, boot, swap, and temporary backup copies of the btrfs > (e.g. before running btrfsck) have to live on the same physical drives > as the btrfs filesystems. Let me to summrize 1) btrfs-single-disk on lvm works fine 2) btrfs-w/multiple-disk on lvm works fine 3) btrfs-single-disk on lvm works fine even with snapshot 4) btrfs-w/multiple-disk doesn't work with lvm AND snapshot However I still doesn't understood why you want btrfs-w/multiple disk over LVM ? > >>>>> and mounting the filesystem fails at 3. >>>> Are you sure ? >>> >>> Yes, I'm sure. I've had to replace filesystems destroyed this way. In a previous email you wrote: >> Multi-device btrfs fails at 2, So I assumed that the point 3 onwards were related to a "single-disk" btrfs. [...] -- gpg @keyserver.linux.it: Goffredo Baroncelli Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5