From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:53865) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROrm4-0003D3-Ui for qemu-devel@nongnu.org; Fri, 11 Nov 2011 09:08:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ROrm3-0003It-OA for qemu-devel@nongnu.org; Fri, 11 Nov 2011 09:08:08 -0500 Received: from mail-gy0-f173.google.com ([209.85.160.173]:37978) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ROrm3-0003Io-I2 for qemu-devel@nongnu.org; Fri, 11 Nov 2011 09:08:07 -0500 Received: by gyb11 with SMTP id 11so3295861gyb.4 for ; Fri, 11 Nov 2011 06:08:06 -0800 (PST) Message-ID: <4EBD2C42.9010109@codemonkey.ws> Date: Fri, 11 Nov 2011 08:08:02 -0600 From: Anthony Liguori 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; format=flowed 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: Kevin Wolf , Stefan Hajnoczi , Juan Quintela , qemu-devel , Avi Kivity , Christoph Hellwig On 11/11/2011 03:55 AM, Daniel P. Berrange wrote: > 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. It might make more sense to make it a property of the storage pool. That is, a storage pool should have a notion of whether it supports migration and what constraints (if any) are given on its migration support. Regards, Anthony Liguori > > Daniel