From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60312) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VcDIo-0006BW-Hy for qemu-devel@nongnu.org; Fri, 01 Nov 2013 07:54:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VcDIi-0007vF-IE for qemu-devel@nongnu.org; Fri, 01 Nov 2013 07:54:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16145) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VcDIi-0007vB-AO for qemu-devel@nongnu.org; Fri, 01 Nov 2013 07:54:04 -0400 Date: Fri, 1 Nov 2013 07:53:59 -0400 From: Jeff Cody Message-ID: <20131101115359.GB17499@localhost.localdomain> References: <201311010604.19768.hahn@univention.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201311010604.19768.hahn@univention.de> Subject: Re: [Qemu-devel] VHD suport in QEMU? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philipp Hahn Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, xen-devel@lists.xen.org On Fri, Nov 01, 2013 at 06:04:19AM +0100, Philipp Hahn wrote: > Hello, > > sorry for high-jacking this thread, but I have a questing regarding VHD (without the X): Xen-4.3 switched to upstream QEMUs support for VHD. The dropped their own VHD implementation in blktap2, which supported backing chains, which QEMU currently doesn't. The Xen implementation (xen/tools/blktap2/vhd/lib/ is BSD 3 clause) also supports some kind of journal. > 1. Does someone know if the journal support for VHD is somehow related to VHDX? I don't believe it is. Despite the similarity in names, VHD and VHDX are completely different formats. I just went and looked at Xen's libvhd-journal, and per my understanding it is a journal written into a separate file, not related to the actual VHD spec itself. It appears to be used by the VHD utility tools, when updating a VHD image file with operations such as resize, etc.., so they can write a finalized bitmap of all header/metadata changes at once to minimize any potential corruption. Jeff