Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?

[Dr. David Alan Gilbert]

* Richard W.M. Jones (address@hidden) wrote:
> On Fri, May 18, 2018 at 06:09:56PM +0100, Daniel P. Berrangé wrote:
> > The closest to a cross-hypervisor standard is OVF which can store
> > metadata about required hardware for a VM. I'm pretty sure it does
> > not have the concept of machine types, but maybe it has a way for
> > people to define metadata extensions. Since it is just XML at the
> > end of the day, even if there was nothing official in OVF, it would
> > be possible to just define a custom XML namespace and declare a
> > schema for that to follow.
> 
> I have a great deal of experience with the OVF "standard".
> TL;DR: DO NOT USE IT.

In addition to the detail below, from reading DMTF's OVF spec (DSP0243 v
2.1.1) I see absolutely nothing specifying hardware type.
Sure it can specify size of storage, number of ether cards, MAC
addresses for them etc - but I don't see any where specify the type of 
emualted system.

Dave

> Long answer copied from a rant I wrote on an internal mailing list a
> while back:
> 
>   Don't make the mistake of confusing OVF for a format.  It's not,
>   there are at least 4 non-interoperable OVF "format"s around:
> 
>    - 2 x oVirt OVF
>    - VMware's OVF used in exported OVA files
>    - VirtualBox's OVF used in their exported OVA files
> 
>   These are all different and do not interoperate *at all*.  So before
>   you decide "let's parse OVF", be precise about which format(s) you
>   actually want to parse.
> 
>   Also OVF is a hideous format.  Many fields are obviously internal data
>   dumps of VMware structures, complete with internal VMware IDs instead
>   of descriptive names.  Where there are descriptive names, they use
>   English strings instead of keywords, like: 
> <rasd:AllocationUnits>MetaBytes</>
>   or my particular WTF favourite, a meaningful field which references
>   English (only) Wikipedia:
> 
>     <Disk ovf:format="http://en.wikipedia.org/wiki/Byte";>
> 
>   File references are split over two places, and there are other
>   examples where data is needlessly duplicated or it's unclear what data
>   is supposed to be.
> 
>   Of course VMware Inc. are not stupid enough to use this format for
>   their own purposes.  They use a completely different format (VMX)
>   which is a lot like YAML.
> 
> Rich.
> 
> -- 
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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--
Dr. David Alan Gilbert / address@hidden / Manchester, UK