From owner-freebsd-stable@FreeBSD.ORG Tue May 17 11:29:54 2011 Return-Path: Delivered-To: stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9A45F106564A for ; Tue, 17 May 2011 11:29:54 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from qmta06.westchester.pa.mail.comcast.net (qmta06.westchester.pa.mail.comcast.net [76.96.62.56]) by mx1.freebsd.org (Postfix) with ESMTP id 4690E8FC1A for ; Tue, 17 May 2011 11:29:53 +0000 (UTC) Received: from omta24.westchester.pa.mail.comcast.net ([76.96.62.76]) by qmta06.westchester.pa.mail.comcast.net with comcast id kbMw1g0031ei1Bg56bVuEL; Tue, 17 May 2011 11:29:54 +0000 Received: from koitsu.dyndns.org ([67.180.84.87]) by omta24.westchester.pa.mail.comcast.net with comcast id kbVt1g0091t3BNj3kbVt4f; Tue, 17 May 2011 11:29:54 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id 1BB38102C19; Tue, 17 May 2011 04:29:52 -0700 (PDT) Date: Tue, 17 May 2011 04:29:52 -0700 From: Jeremy Chadwick To: Andriy Gapon Message-ID: <20110517112952.GA48610@icarus.home.lan> References: <20110517073029.GA44359@icarus.home.lan> <4DD25264.8040305@FreeBSD.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DD25264.8040305@FreeBSD.org> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: Charles Sprickman , stable@FreeBSD.org Subject: Re: 8.1R possible zfs snapshot livelock? X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 May 2011 11:29:54 -0000 On Tue, May 17, 2011 at 01:48:04PM +0300, Andriy Gapon wrote: > on 17/05/2011 10:30 Jeremy Chadwick said the following: > > On Tue, May 17, 2011 at 02:43:44AM -0400, Charles Sprickman wrote: > >> Does this sound familiar to anyone running ZFS with snapshots? > > > > Yes, and is exactly why I don't use them. :-) > > You put a smiley, but is this an attempt at FUD? I wish it were. I experienced similar behaviour to Charles during the early 8.x days (possibly 8.1-RELEASE, I forget; I may be thinking of 8.0?) where ZFS snapshots would occasionally result in the kernel deadlocking on ZFS-bound I/O. The kernel was alive/responsive to some degree but ZFS I/O would just indefinitely stall at that point, requiring a full system reset. No disk or controller problems (same hardware I'm using today actually!). I believe there were commits and improvements for snapshotting committed between 8.1-RELEASE and 8.2-RELEASE, but I haven't bothered to test them. The experience left a very bad taste in my mouth and as such I have avoided ZFS snapshots since. I'd be willing to try them again assuming someone can at least confirm that there were commits done to address snapshot concerns during the past year or so. But... There are still some outstanding incidents that directly pertain to ZFS snapshots, or are "related" to ZFS snapshots (meaning things like send/recv which are commonly used alongside snapshots), which I remember reading about but really saw no answer to: * ZFS send | ssh zfs recv results in ZFS subsystem hanging; 8.1-RELEASE; February 2011: http://lists.freebsd.org/pipermail/freebsd-fs/2011-February/010602.html * Kernel panic during heavy disk I/O while "zfs recv" being used simultaneously; CURRENT (so ZFS v28?); April 2011: http://lists.freebsd.org/pipermail/freebsd-fs/2011-April/011155.html * ZFS snapshots taking an extremely long time to be deleted; RELENG_8_1; February 2011: http://lists.freebsd.org/pipermail/freebsd-fs/2011-February/010797.html * "zfs destroy -r" not working on filesystem-level snapshots but works on pool-level snapshots; RELENG_8 with ZFS v28 patch (and is specific to ZFS v28 given the info); May 2011: http://lists.freebsd.org/pipermail/freebsd-fs/2011-May/011412.html Sorry to just rattle off a bunch of URLs and issues at once; it's not my intention to slander work on ZFS or anything even remotely like that. I'm just wondering given the number of problem reports that seem to come in about snapshot or snapshot-related ZFS stuff, where we stand on these? This is mainly for Charles' benefit and not so much mine (our rsnapshot/rsync-based backups work great for us at this time, sans the stomping of atime). -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP 4BD6C0CB |