From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59121) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UpK73-000202-9j for qemu-devel@nongnu.org; Wed, 19 Jun 2013 11:16:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UpK71-0005Ld-Ps for qemu-devel@nongnu.org; Wed, 19 Jun 2013 11:15:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28204) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UpK71-0005LN-9T for qemu-devel@nongnu.org; Wed, 19 Jun 2013 11:15:55 -0400 Date: Wed, 19 Jun 2013 17:15:52 +0200 From: Kevin Wolf Message-ID: <20130619151552.GL2934@dhcp-200-207.str.redhat.com> References: <201306191602.02983.hahn@univention.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201306191602.02983.hahn@univention.de> Subject: Re: [Qemu-devel] backing file support for vpc/vhd ? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philipp Hahn Cc: qemu-devel Am 19.06.2013 um 16:02 hat Philipp Hahn geschrieben: > Hello, > > while working on a Xen-VM I noticed that qemu-img does not support the backing file mechanism of vpc/vhd files, but Xens blktap2 does; it has a libvhd and some tools to create and modify vpc/vhd files: > [...] > > Is the lack of support for backing files in vpc/vjd in qemu just a question of time / interest, are there technical problems, or are there some political issues? Nobody wrote the code, that's all. Read-only support should be almost trivial, and for read-write we'd have to add some real code to deal with the block bitmaps (without backing files we get away with what is mostly a slow fake implementation). Kevin