On 2018-06-06 13:37, Dr. David Alan Gilbert wrote: > * Max Reitz (mre...@redhat.com) wrote: >> On 2018-06-06 13:19, Michal Suchánek wrote: >>> On Wed, 6 Jun 2018 13:02:53 +0200 >>> Max Reitz <mre...@redhat.com> wrote: >>> >>>> On 2018-06-06 12:32, Michal Suchánek wrote: >>>>> On Tue, 29 May 2018 12:14:15 +0200 >>>>> Max Reitz <mre...@redhat.com> wrote:
[...] >>>>>> Unless I have got something terribly wrong (which is indeed a >>>>>> possibility!), to me this proposal means basically to turn qcow2 >>>>>> into (1) a VM description format for qemu, and (2) to turn it into >>>>>> an archive format on the way. >>>>> >>>>> And if you go all the way you can store multiple disks along with >>>>> the VM definition so you can have the whole appliance in one file. >>>>> It conveniently solves the problem of synchronizing snapshots across >>>>> multiple disk images and the question where to store the machine >>>>> state if you want to suspend it. >>>> >>>> Yeah, but why make qcow2 that format? That's what I completely fail >>>> to understand. >>>> >>>> If you want to have a single VM description file that contains the VM >>>> configuration and some qcow2/raw/whatever files along with it for the >>>> guest disk data, sure, go ahead. But why does the format of the whole >>>> thing need to be qcow2? >>> >>> Because then qemu can access the disk data from the image directly >>> without any need for extraction, copying to different file, etc. >> >> This does not explain why it needs to be qcow2. There is absolutely no >> reason why you couldn't use qcow2 files in-place inside of another file. > > Because then we'd have to change the whole stack to take advantage of > that. Adding a feature into qcow2 means nothing else changes. Because it's a hack, right. Storing binary data in a qcow2 file, completely ignoring it in qemu (and being completely unusable to any potential other users of the qcow2 format[1]) and only interpreting it somewhere up the stack is a hack. That is not necessarily a negative point, hacks can work wonderfully well, and they usually are simple, that is correct. But the thing is that I feel like people have grand visions of what to get out of this. Imagine, a single file that can configure all and any VM! But hacks usually only solve a single issue. Once you try to extend a hack, it breaks down and becomes insufficient. If we want a grand vision where a single file stores the whole VM, why not invest the work and make it right from the start? Max [1] Yes, I concede that there are probably no other users of qcow2. But please forgive me for assuming that qcow2 was in a sense designed to be a rather general image format that not only qemu could use.
signature.asc
Description: OpenPGP digital signature
