Re: Hosting recommendations ... ?

[Brandon Martin <lists.nanog () monmotha net>]

On 1/19/21 12:56 PM, Bryan Holloway wrote:
> I'm very curious about your assertion:
>
> Is nested virtualization really a thing?
>
> I mean, I'm not exactly trying to render Pixar's latest movie ... just 
> trying to push some bits around (light web-sites, some e-mail ...)
>
> It just seems inherently prone to issues.
>
> Could you back this up with any white-papers or documentation on the 
> subject? I'm genuinely interested ...

With KVM, if you have a recent kernel and qemu, it pretty much "just 
works" on supported hardware.  AFAIK Xen supports "Xen on Xen", too, but 
I haven't used it and don't know much about it.

The use case is pretty much exactly this.  You (the product consumer) 
are handed a product that amounts to a virtual machine on somebody 
else's $BIGBOX.  You want to deploy multiple virtual machines where you 
have direct control over their lifecycle, configuration, etc. and can 
bring in additional I/O resources, etc. at the hypervisor level 
(consider that, with KVM, the Linux kernel basically IS the hypervisor). 
 So, you run one or more VMs inside the top level VM that you're handed.

It's full of lots of little wiggles and can be a pain to maintain if you 
have visibility into both levels of the equation, but it does seem to 
work and is surprisingly performant.

See e.g. https://tips.graphica.com.au/nested-kvm/
--
Brandon Martin