From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Bashkirtsev Subject: Re: Ceph and KVM live migration Date: Sun, 01 Jul 2012 11:45:50 +0930 Message-ID: <4FEFB2D6.6010603@bashkirtsev.com> References: <4FEF9CF1.6030008@bashkirtsev.com> <4FEFA53F.4020503@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail.logics.net.au ([150.101.56.178]:42318 "EHLO mail.logics.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754507Ab2GACQa (ORCPT ); Sat, 30 Jun 2012 22:16:30 -0400 In-Reply-To: <4FEFA53F.4020503@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Josh Durgin Cc: ceph-devel@vger.kernel.org On 01/07/12 10:47, Josh Durgin wrote: > On 06/30/2012 05:42 PM, Vladimir Bashkirtsev wrote: >> Dear all, >> >> Currently I testing KVMs running on ceph and particularly testing recent >> cache feature. Performance is of course vastly improved but still have >> occasional KVM hold ups - not sure who is at blame ceph of KVM. But I >> will deal with it later. Right now I've got myself a question which I >> could not get answered myself: if I do live migration of KVM while there >> some uncommitted data in ceph cache will this cache be committed prior >> cut-over to another host? Reading through the list I've got an >> impression that it may be left uncommitted and thus it may cause data >> corruption. I just would like a simple confirmation if code which >> commits cache on cut-over to new host does exist and no data corruption >> due to RBD cache+live migration should happen. >> >> Regards, >> Vladimir > > QEMU does a flush on all the disks when it stops the guest on the > original host, so there will be no uncommitted data in the cache. > > Josh Thank you for quick and precise answer. Now when I actually attempted to live migrate ceph based VM I get: Unable to migrate guest: Invalid relative path 'rbd/mail.logics.net.au:rbd_cache=true': Invalid argument I guess KVM does not like having :rbd_cache=true (migration works without it). I know that it is most likely KVM problem but still decided to ask here in case if you know about it. Any ideas how to fix it? Regards, Vladimir