Hi @Anonymous ,
let's take it like this: "Nested Virtualization in addition with a combination of different virtualization solutions doesn't speed things up" ;-)
The advantage in Azure is: Resizing a virtual machine for testing is easy, fast and doesn't cost that much.
I would just resize the Azure VM at least to the double and do some tests.
After the tests are done decreasing the size of the VM is easy as well.
Also it might be interesting to find the real cause for the lag of performance. It's the Azure VM (CPU, RAM, Disk) or maybe it's related to the Oracle Virtual Box as a nested virtualization.
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Regards
Andreas Baumgarten