From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm Date: Mon, 24 May 2010 14:56:29 +0300 Message-ID: <4BFA696D.2060606@redhat.com> References: <20100519192222.GD61706@ncolin.muc.de> <4BF5A9D2.5080609@codemonkey.ws> <4BF91937.2070801@redhat.com> <87wrutg4dk.wl%morita.kazutaka@lab.ntt.co.jp> <4BFA5D96.3030603@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , Christian Brunner , Blue Swirl , kvm@vger.kernel.org, qemu-devel@nongnu.org, ceph-devel@vger.kernel.org To: MORITA Kazutaka Return-path: In-Reply-To: Sender: ceph-devel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 05/24/2010 02:42 PM, MORITA Kazutaka wrote: > >> The server would be local and talk over a unix domain socket, perhaps >> anonymous. >> >> nbd has other issues though, such as requiring a copy and no support for >> metadata operations such as snapshot and file size extension. >> >> > Sorry, my explanation was unclear. I'm not sure how running servers > on localhost can solve the problem. > The local server can convert from the local (nbd) protocol to the remote (sheepdog, ceph) protocol. > What I wanted to say was that we cannot specify the image of VM. With > nbd protocol, command line arguments are as follows: > > $ qemu nbd:hostname:port > > As this syntax shows, with nbd protocol the client cannot pass the VM > image name to the server. > We would extend it to allow it to connect to a unix domain socket: qemu nbd:unix:/path/to/socket The server at the other end would associate the socket with a filename and forward it to the server using the remote protocol. However, I don't think nbd would be a good protocol. My preference would be for a plugin API, or for a new local protocol that uses splice() to avoid copies. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.