From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58950) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZgZBV-0000aP-Fr for qemu-devel@nongnu.org; Mon, 28 Sep 2015 10:13:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZgZBU-0003pg-LE for qemu-devel@nongnu.org; Mon, 28 Sep 2015 10:13:41 -0400 Sender: Paolo Bonzini References: From: Paolo Bonzini Message-ID: <56094B0F.7030900@redhat.com> Date: Mon, 28 Sep 2015 16:13:35 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 3/3] block: mirror - zero unallocated target sectors when zero init not present List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody , qemu-devel@nongnu.org Cc: kwolf@redhat.com, qemu-block@nongnu.org, stefanha@redhat.com On 28/09/2015 05:29, Jeff Cody wrote: > This only occurs under two conditions: > > 1. 'mode' != "existing" > 2. bdrv_has_zero_init(target) == NULL > I'm not sure if mode != "existing" actually matters. I think what actually matters is sync == "full". The reasons are: 1) with sync != "full", unallocated target sectors should remain unallocated on the destination because they are supposed to point to the backing file. 2) even with mode == "existing" you expect the data to be consistent at the end of the mirroring Paolo