From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:34710) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UMdkR-0006Z9-Lw for qemu-devel@nongnu.org; Mon, 01 Apr 2013 08:22:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UMdkQ-0007AA-9h for qemu-devel@nongnu.org; Mon, 01 Apr 2013 08:22:03 -0400 Received: from mail.avalus.com ([2001:41c8:10:1dd::10]:32833) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UMdkQ-00079n-4F for qemu-devel@nongnu.org; Mon, 01 Apr 2013 08:22:02 -0400 Date: Mon, 01 Apr 2013 13:21:45 +0000 From: Alex Bligh Message-ID: <7029962A8C6EFDBC98B51E44@nimrod.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Subject: [Qemu-devel] Adding a persistent writeback cache to qemu Reply-To: Alex Bligh List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Alex Bligh I'd like to experiment with adding persistent writeback cache to qemu. The use case here is where non-local storage is used (e.g. rbd, ceph) using the qemu drivers, together with a local cache as a file on a much faster locally mounted device, for instance an SSD (possibly replicated). This would I think give a similar performance boost to using an rbd block device plus flashcache/dm-cache/bcache, but without introducing all the context switches and limitations of having to use real block devices. I appreciate it would need to be live migration aware (worst case solution: flush and turn off caching during live migrate), and ideally be capable of replaying a dirty writeback cache in the event the host crashes. Is there any support for this already? Has anyone worked on this before? If not, would there be any interest in it? -- Alex Bligh