From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:58873) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R4BAo-00020d-BR for qemu-devel@nongnu.org; Thu, 15 Sep 2011 08:36:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1R4BAk-0001nx-2J for qemu-devel@nongnu.org; Thu, 15 Sep 2011 08:36:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10807) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R4BAj-0001ng-RG for qemu-devel@nongnu.org; Thu, 15 Sep 2011 08:36:06 -0400 From: Orit Wasserman Date: Thu, 15 Sep 2011 15:34:59 +0300 In-Reply-To: <4E71E854.10302@redhat.com> References: <1315628610-28222-1-git-send-email-ronniesahlberg@gmail.com> <1315628610-28222-2-git-send-email-ronniesahlberg@gmail.com> <20110912091408.GA3465@stefanha-thinkpad.localdomain> <4E71956B.6030902@redhat.com> <4E71BBE3.5000207@redhat.com> <4E71C146.6070406@redhat.com> <4E71E4B2.9060304@redhat.com> <4E71E854.10302@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Message-ID: <1316090109.29180.43.camel@dhcp-1-120.tlv.redhat.com> Mime-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] This patch adds a new block driver : iSCSI List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, Stefan Hajnoczi , dlaor@redhat.com, qemu-devel@nongnu.org, fujita.tomonori@lab.ntt.co.jp, Ronnie Sahlberg , hch@lst.de On Thu, 2011-09-15 at 13:58 +0200, Paolo Bonzini wrote: > On 09/15/2011 01:42 PM, Dor Laor wrote: > >> > >> However, iSCSI is a complex protocol and a complex suite of tools. With > >> a simpler set of tools such as qemu-nbd/nbd, you can for example tunnel > >> data over the libvirt connection. Possibly with encryption. Also, with > >> iSCSI you're tied to raw, while qemu-nbd lets you use qcow2. > > > > My main motivation for external iScsi is to provide qemu operations w/ > > non shared storage. Things like streaming an image w/o shared storage or > > block live migration can be done where the src host exposes iscsi target > > and the destination is the initiator. In case of qcow2, every snapshot > > in the chain should be exposed as a separate LUN. The idea is to ignore > > the data in the guest image and treat it as opaque. > > Then you need an iSCSI *target* that understands qcow2, like qemu-nbd > but for iSCSI... that's exactly the thing you were worried about > implementing. Not really , this is just part of the target configuration. For each file in the chain we create a lun in the target that is backed by the file and we number the luns in chronological order (base is lun 1) . you can look at a tgtd configuration here http://wiki.qemu.org/Features/LiveBlockMigration#Example_single_base_master_image. Orit > > (Of course you could use qemu-nbd and expose /dev/nbd* via iSCSI, but it > starts looking like an exercise in adding layers of indirections! :)). > > Paolo >