Re: [libvirt] [Qemu-devel] live snapshot wiki updated

On Wed, Jul 20, 2011 at 10:26:49AM +0200, Jes Sorensen wrote: > On 07/19/11 18:47, Daniel P. Berrange wrote: >> On Tue, Jul 19, 2011 at 04:30:19PM +0200, Jes Sorensen wrote: >>> On 07/19/11 16:24, Eric Blake wrote: >>>> Besides, I feel that having a well-documented file format, so that >>>> independent applications can both parse the same file with the same >>>> semantics by obeying the file format specification, is a good design goal. >>> >>> We all know that documentation is rarely uptodate, new features may not >>> get added and libvirt will never be able to keep up. The driver for a >>> file format belongs in QEMU and nowhere else. >> >> This would be possible if QEMU to provide a libblockformat.so library >> which allowed apps to extract metadata from file formats using a stable >> API. > > There is no reason for libvirt or any external process to mess about > with the internals of image files. You have the same problem if the > image file is encrypted. Just repeating "libvirt doesn't need todo this" many times doesn't make it true. I have described why we need to read the disk image to determine its backing files ahead of QEMU being launched quite clearly.