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by vlovich123 1582 days ago
Can you explain this? Afaict hyper-v is the same as VMware or virtual box where you have a host OS and multiple guest OSes (which makes sense because you still need something to run the OS drivers). It sounds like what you’re implying is it behaves differently but I’m not sure how. Can you elaborate?
2 comments
bpye 1582 days ago
Hyper-V is similar to Xen. The hypervisor runs on bare metal, the Windows root is akin to your dom0 on Xen, and your guests are your domU.
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vlovich123 1582 days ago
Ok, but then I still don’t understand this piece:

> If they are running on Hyper-V on Azure, there is no underlying kernel doing anything.

In a Xen model as I understand it, the dom0 kernel is still actually responsible for talking to all the hardware directly and presenting a virtualized implementation that Xen can mux other guests on, no? So there’s still a kernel there and it’s doing quite a bit of work, no?

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bpye 1581 days ago
The dom0 kernel is responsible for talking to devices such as a disk or a NIC, yes, be that Linux, NT, *BSD, etc. The hypervisor is typically responsible for enforcing isolation of compute, memory, etc. The line does blur - for example Hyper-V may be configured with something called the “root scheduler” with which NT is responsible for scheduling virtual CPUs [0] - though the hypervisor is still enforcing the isolation.

[0] - https://docs.microsoft.com/en-us/windows-server/virtualizati...

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pjmlp 1582 days ago
Windows runs as guest OS on top of Hyper-V as well, it is a type 1 hypervisor.

Basically when you activate Hyper-V, you will be getting one VM running where the host is only a guest with special privileges known as root partition.

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