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Hyper-V on Windows 10 differs from Hyper-V on Windows Server in features and memory management, as stated in Microsoft docs for Hyper-V:

There are some features that work differently in Hyper-V on Windows than they do in Hyper-V running on Windows Server.

Hyper-V features only available on Windows Server:

  • Live migration of virtual machines from one host to another
  • Hyper-V Replica
  • Virtual Fiber Channel
  • SR-IOV networking
  • Shared .VHDX

Hyper-V features only available on Windows 10:

  • Quick Create and the VM Gallery
  • Default network (NAT switch)

The memory management model is different for Hyper-V on Windows. On a server, Hyper-V memory is managed with the assumption that only the virtual machines are running on the server. In Hyper-V on Windows, memory is managed with the expectation that most client machines are running software on host in addition to running virtual machines.

But the last paragraph is a bit confusing to me. Does it mean that Hyper-V on Windows Server is Type 1 Hypervisor, and on Windows 10 Type 2 Hypervisor?

ebu_sho
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    By the original 1970s definitions, virtually all modern hypervisors are Type 2. That distinction is not useful for much of anything today. – Michael Hampton Jul 29 '18 at 12:52
  • It is more useful to get a block diagram of the components including the kernels, scheduler, and drivers. That is much more informative than a simplistic type 1 or type 2 category. – John Mahowald Jul 29 '18 at 13:02

2 Answers2

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Does it mean that Hyper-V on Windows Server is Type 1 Hypervisor, and on Windows 10 Type 2 Hypervisor?

No. It means that the memory tuning assumes on Windows 10 the root partition (VM) runs apps, and not if Hyper-V Server.

The root partition is a VM, see the Hyper-V Architecture diagram.

People love to debate type 1 and type 2 for some reason. Here's one of the more informed debates, via Hacker News:

on init, the Hyper-V driver hijacks the running Windows instance, schedules it as the 'root partition', and runs it like just another VM.

unlike 'child partitions', the root partition still has non-virtualized drivers, which run unimpeded by privileged instruction traps.

when a child partition (guest VM) is started, it's scheduled as a peer to the root. its Virtual Processors (VPs) run alongside the root partition's VPs.

when the child partition traps into the hypervisor, or uses one of the enlightened drivers, the hypervisor dispatches a bus request to the root partition, which handles the IRQ using a Virtual Service Provider implemented by the host Windows kernel.

so the hypervisor is kind of a bridge between the host Windows and the child VMs, but the host Windows actually runs as a sort of privileged VM itself, just one with full hardware access and scheduling priority.

John Mahowald
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  • Great detailed description! Yeah, both 10 and Server (and previously 8/8.1) are type-1 hyper-visors, with the host/management OS running on top of the hyper-visor just like the guests, after all in regard to hyper-v they're both running the same code base, not two different versions of it, they're just tuned to how you'd actually use them (and feature limited obviously in the case of 10) – Keith Langmead Aug 01 '18 at 21:09
  • That description is slightly out of date. For the last several Windows releases, the hypervisor itself boots before the root partition. – Jake Oshins Nov 05 '18 at 17:41
  • Any specifics you can cite about the exact order of init, please raise an issue on Microsoft's documentation. The point I was trying to make is that there is both a hypervisor bridging partitions and a kernel running with hardware access plus possibly user applications. – John Mahowald Nov 06 '18 at 13:56
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No, not necesariliy, just that hter are some more features.

  • QUick create is IMHO neven a Hyper-V core feature - it is additional UI, nothing in the hypervisor.

  • Same with Default network as a NAT switch. That is just something you could setup yourself on a server (using RRAS NAT as NAT mechanism if you have to).

Both target the different use case - Server is more to be used a a server, while in Windows it is a use case that benefits from a windwos based gallery-

TomTom
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