From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45032) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YpFTW-00067H-NZ for qemu-devel@nongnu.org; Mon, 04 May 2015 08:27:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YpFTT-0007IS-Cw for qemu-devel@nongnu.org; Mon, 04 May 2015 08:27:54 -0400 Received: from mail-wi0-x232.google.com ([2a00:1450:400c:c05::232]:36350) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YpFTT-0007IM-76 for qemu-devel@nongnu.org; Mon, 04 May 2015 08:27:51 -0400 Received: by wizk4 with SMTP id k4so119525165wiz.1 for ; Mon, 04 May 2015 05:27:50 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <554765C2.7010900@redhat.com> Date: Mon, 04 May 2015 14:27:46 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <5545D979.1090303@rdsoftware.de> <55475499.1040708@redhat.com> In-Reply-To: <55475499.1040708@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Comparison of virtual disks? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz , Erik Rull , "qemu-devel@nongnu.org" On 04/05/2015 13:14, Max Reitz wrote: > I'm sorry, but I don't know whether such a chart exists (the closest > thing I know is http://en.wikipedia.org/wiki/Category:Disk_images - > which is not very close...). However, the general assumption we as > developers are working with is that if the user's top priority is > performance, they should use raw; and if they want to use all of the > features qemu's block layer provides, they should use qcow2. All other > formats are implemented merely for compatibility and ideally they should > not be used for running VMs, but only for converting them to qcow2 using > qemu-img convert. In addition to this, there are a bunch of image formats that have good read performance: I can think of vhdx, vmdk, vdi. These can be used as backing images for qcow2, for example the virt-v2v tool uses this trick to convert Hyper-V and VMware images without copying them first. Paolo