From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:34481) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROnsr-0005TL-9z for qemu-devel@nongnu.org; Fri, 11 Nov 2011 04:58:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ROnsq-0004qe-8u for qemu-devel@nongnu.org; Fri, 11 Nov 2011 04:58:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40399) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROnsp-0004pG-W0 for qemu-devel@nongnu.org; Fri, 11 Nov 2011 04:58:52 -0500 Message-ID: <4EBCF290.4070503@redhat.com> Date: Fri, 11 Nov 2011 11:01:52 +0100 From: Kevin Wolf MIME-Version: 1.0 References: <4EBC683C.7090700@codemonkey.ws> <4EBCED0C.80601@redhat.com> <20111111095524.GB8472@redhat.com> In-Reply-To: <20111111095524.GB8472@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Storage requirements for live migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Stefan Hajnoczi , Juan Quintela , qemu-devel , Avi Kivity , Christoph Hellwig Am 11.11.2011 10:55, schrieb Daniel P. Berrange: > On Fri, Nov 11, 2011 at 10:38:20AM +0100, Kevin Wolf wrote: >> Am 11.11.2011 01:11, schrieb Anthony Liguori: >>> I did a brain dump of my understanding of the various storage requirements for >>> live migration. I think it's accurate but I may have misunderstand some details >>> so I would appreciate review. >>> >>> I think given sections (1) and (2), the only viable thing is to require >>> cache=none unless we get new interfaces to flush caches. >> >> Yes, I think we should strongly recommend cache=none/directsync, but not >> enforce it. As you said, for clustered filesystems other options should >> work, so we should allow users to choose to make use of that. > > WRT libvirt, we have a concept of 'tainting' for guests. We set taint > flags whenever the management application requests a config, or performs > an action that we know to be potentially dangerous. These end up as log > messages in the per-guest logfile, so when users report bugs we can see > from the log that something "bad" has been done to the guest. > > At the very least, it sounds like we should make libvirt mark guests as > tainted, if they have been migrated with cache != none, so this is easily > identifiable by BZ support people. > > We might also want to make a libvirt host level config option to allow > host admins forbid migration without cache=none. Yes, I think this would be a good approach. Kevin