From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46801) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uby3s-0001ci-8u for qemu-devel@nongnu.org; Mon, 13 May 2013 15:05:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uby3q-0006T9-6f for qemu-devel@nongnu.org; Mon, 13 May 2013 15:05:28 -0400 Received: from mail-we0-x22f.google.com ([2a00:1450:400c:c03::22f]:41236) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uby3p-0006T5-VF for qemu-devel@nongnu.org; Mon, 13 May 2013 15:05:26 -0400 Received: by mail-we0-f175.google.com with SMTP id p57so6739826wes.34 for ; Mon, 13 May 2013 12:05:25 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <51913970.4050807@redhat.com> Date: Mon, 13 May 2013 21:05:20 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] drive-mirror sync points List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wolfgang Richter Cc: qemu-devel Il 13/05/2013 19:50, Wolfgang Richter ha scritto: > Paolo/anyone who knows - > > Are drive-mirror sync points (NBD flush commands) reflecting guest write > barriers? Are guest write barriers respected by drive-mirror? If so, > that would make drive-mirror much more palatable for disk introspection > work (a drop-in usable feature of QEMU!). Kind of. Sync points reflect points where the destination image is a copy of the source image at some point in time. Destination image write barriers hence reflect places where the destination image is consistent with guest write barriers, but not all guest write barriers become destination image write barriers. Paolo