From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39821) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VGTfD-0006Jo-T2 for qemu-devel@nongnu.org; Mon, 02 Sep 2013 08:55:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VGTf9-0001G1-0u for qemu-devel@nongnu.org; Mon, 02 Sep 2013 08:55:27 -0400 Received: from nodalink.pck.nerim.net ([62.212.105.220]:58839 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VGTf8-0001Fv-OT for qemu-devel@nongnu.org; Mon, 02 Sep 2013 08:55:22 -0400 Date: Mon, 2 Sep 2013 14:57:23 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20130902125722.GG5073@irqsave.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v3 0/8] block: drive-backup live backup command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: dietmar@proxmox.com Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com I don't see the point of using hashes. Using hashes means that at least one extra read will be done on the targe= t to compute the candidate target hash. It's bad for a cloud provider where IOs count is a huge cost. Another structure to replace a bitmap (smaller on the canonical case) wou= ld be a block table as described in the Hystor paper: www.cse.ohio-state.edu/~fchen/paper/papers/ics11.pdf Best regards Beno=EEt