From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pigeon.gentoo.org ([208.92.234.80] helo=lists.gentoo.org) by finch.gentoo.org with esmtp (Exim 4.60) (envelope-from ) id 1MxUi3-00041b-Ip for garchives@archives.gentoo.org; Mon, 12 Oct 2009 23:53:47 +0000 Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 959EEE07EA; Mon, 12 Oct 2009 23:53:46 +0000 (UTC) Received: from vms173005pub.verizon.net (vms173005pub.verizon.net [206.46.173.5]) by pigeon.gentoo.org (Postfix) with ESMTP id 7AF75E07EA for ; Mon, 12 Oct 2009 23:53:46 +0000 (UTC) Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-dev@lists.gentoo.org Reply-to: gentoo-dev@lists.gentoo.org MIME-version: 1.0 Content-type: text/plain; charset=UTF-8; format=flowed Received: from gw.thefreemanclan.net ([96.245.54.239]) by vms173005.mailsrvcs.net (Sun Java(tm) System Messaging Server 6.3-7.04 (built Sep 26 2008; 32bit)) with ESMTPA id <0KRF00BDZED80UE7@vms173005.mailsrvcs.net> for gentoo-dev@lists.gentoo.org; Mon, 12 Oct 2009 18:53:38 -0500 (CDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by gw.thefreemanclan.net (Postfix) with ESMTP id D00991759DA0 for ; Mon, 12 Oct 2009 19:53:31 -0400 (EDT) Message-id: <4AD3C17B.7030602@gentoo.org> Date: Mon, 12 Oct 2009 19:53:31 -0400 From: Richard Freeman User-Agent: Thunderbird 2.0.0.23 (X11/20090912) To: gentoo-dev@lists.gentoo.org Subject: Re: [gentoo-dev] Init systems portage category References: <20091012093942.08ef453a@dante> <173442fb4ce538d8895eb52554f0b780@localhost> <13ecafe4c66b8ddaf0c70ef84ecb62b8@localhost> In-reply-to: <13ecafe4c66b8ddaf0c70ef84ecb62b8@localhost> Content-Transfer-Encoding: quoted-printable X-Archives-Salt: aaa47b36-8835-4793-a2c9-abe2799db76d X-Archives-Hash: 070ae6e398ea6c0a1ca297b84e6c9ce4 Jes=C3=BAs Guerrero wrote: >=20 > In my opinion, if we really want to speak about a way to implement that > kind of snapshoting, we should start thinking about providing a better > integration with lvm, from the root. lvm can take care of the snapshots= on > a non-expensive way, and it would be relatively easy to implement. Howe= ver > a lot of stuff would need to be re-documented, starting from the handbo= ok, > and the init system. LVM snapshotting is extremely wasteful - it has no knowledge of the=20 underlying structure of a filesystem. For example, if I moved all the=20 files around on a fairly full ext3 filesystem, an LVM snapshot would=20 consume the full size of the filesystem. However, a filesystem-level=20 solution wouldn't need to store a single byte of data since nothing=20 actually changed. Also - a snapshot restoration obliterates ALL data on the partition that=20 has changed since the snapshot was taken - so unless the essential files=20 are on a separate partition it won't work out well. LVM snapshots really seem to be a solution to atomic backups - if you=20 unmount, snapshot, and remount a filesystem then you can run a=20 self-consistent backup off of the snapshot with minimal downtime. The=20 wasted space isn't a big deal since the snapshot would be deleted before=20 it grew too far. Finally - I'm not to eager to try out lvm2 again anytime soon - I lost a=20 ton of data when something glitched and wiped out data across multiple=20 lvm partitions. I know that the error must have been in the lvm layer=20 (not md or the filesystem), because when I fscked and repaired one=20 filesystem, another filesystem instantly became hosed (on a separate lvm=20 partition). Somehow the partitions had gotten scrambled together and=20 the fsck was crossing partition boundaries. Plus, dmesg was dumping all=20 kinds of compliants at the md layer about the lvm device trying to=20 access out-of-range clusters. Googling I found a few other reports of=20 similar behavior - it seems extremely rare, but very nasty. Fortunately the most important stuff on my PC was backed up (good=20 planning), but it was still a pain - I lost tons of DVR recordings since=20 I don't back that up (not worth the cost vs the value of the data). Now=20 I just run ext3 on top of md and I haven't had any problems. You're right that btrfs will definitely help. However, being able to=20 create a personal stage1 tarball at will would certainly also be useful,=20 and it wouldn't actually consume much disk space.