From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45620) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XNlt7-0001u9-3i for qemu-devel@nongnu.org; Sat, 30 Aug 2014 12:52:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XNlt2-0005dG-Ko for qemu-devel@nongnu.org; Sat, 30 Aug 2014 12:52:28 -0400 Received: from lputeaux-656-01-25-125.w80-12.abo.wanadoo.fr ([80.12.84.125]:41662 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XNlt2-0005d7-Aw for qemu-devel@nongnu.org; Sat, 30 Aug 2014 12:52:24 -0400 Date: Sat, 30 Aug 2014 18:51:34 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20140830165133.GB2212@irqsave.net> References: <20140829172218.GD16755@irqsave.net> <20140830144641.GM14001@redhat.com> <20140830155343.GA2212@irqsave.net> <20140830160212.GH1302@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20140830160212.GH1302@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] tcmu-runner and QEMU List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: =?iso-8859-1?Q?Beno=EEt?= Canet , kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, pbonzini@redhat.com, agrover@redhat.com The Saturday 30 Aug 2014 =E0 17:02:12 (+0100), Richard W.M. Jones wrote : > On Sat, Aug 30, 2014 at 05:53:43PM +0200, Beno=EEt Canet wrote: > > The Saturday 30 Aug 2014 =E0 15:46:41 (+0100), Richard W.M. Jones wro= te : > > > For the benefit of those who have absolutely no idea what you're > > > talking about, could you write a simpler summary of what you're try= ing > > > to do? > > >=20 > > > Rich. > >=20 > > Hello, > >=20 > > Most cloud providers sell virtualized instances either using Xen or K= VM. > > > > However another trend is to provide bare metal instances for people > > who want the highest CPU and network performance possible.(typicaly > > people doing computation with MPI) > > > > So a cloud end user would need to be able to instanciate a virtual > > machine use it for a while then stop the virtual machine, change the > > hardware type to bare metal and restart the instance while keeping > > using the same boot volume. > > > > QEMU will keep a virtual machine data stored in one of it's numerous > > storage backend format like QCOW2 or QED. > > > > If the cloud provider want to be able to boot QCOW2 or QED images on > > bare metal machines he will need to export QCOW2 or QED images on > > the network. > > > > So far only qemu-nbd allows to do this and it is neither well > > performing nor really convenient to boot on a bare metal machine. >=20 > So I think what you want is a `qemu-iscsi'? ie. the same as qemu-nbd, > but with an iSCSI frontend (to replace the NBD server). >=20 > I think this is an excellent idea, although AIUI iSCSI is a pretty > complex protocol. (I wrote an NBD server, and the protocol is almost > trivial, albeit as you say, performing badly). >=20 > > So summarize I am looking for a way to export QCOW2 or QED image as > > an ISCSI or FCOE targets while keeping all the goodies these format > > provides (taking snapshots for backup, streaming, mirroring). > > > > Reusing LIO code would help tremendously to simplify this task. >=20 > I guess so. Are you planning to integrate bits of LIO into qemu, or > bits of qemu into LIO? >=20 > The latter has been tried various times, without much success. See > the many examples of people trying to make the qemu block driver code > into a separate library, and failing. Paolo pointed me to Andy's current work so I started this discution: http://thread.gmane.org/gmane.linux.kernel/1771465. I know well enough the QEMU block layer to be aware that it's riddled with static variables so I think bits of Andy's current work on top of a qemu-lio command would be the way. >> Writing an iSCSI front end to qemu would be good, but qemu has some > very particular policies about what code can be introduced, so that > could be tricky too ... Where can I read these policies ? Best regards Beno=EEt >=20 > Rich. >=20 > --=20 > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~= rjones > Read my programming and virtualization blog: http://rwmj.wordpress.com > libguestfs lets you edit virtual machines. Supports shell scripting, > bindings from many languages. http://libguestfs.org