@storageninja said in HyperV Partitioning:
My point is that things in the IO path go through that VM. They didn't want to write a full IO driver stack for Hyper-V so they have the VM for that. Compute/Memory doesn't go through it (that I know of), but network and disk IO do. (Otherwise Perfmon wouldn't work as a monitoring solution on the host).
I think you have some misconceptions or misunderstandings regarding the Hyper-V architecture and components... or Hyper-V stack...
This is not true at all, as it actually depends on the OS running in a VM.
Operating systems that already have the integration components baked into their kernel (Enlightened VMs) use their own Hypercalls to communicate directly to the hypervisor, then to the physical hardware.
Only for non-supporeted (older) operating systems, does the "parent partition" intercept the VM communication, emulating Hypercalls. In this case, there are performance degradations as the management OS needs to work as a bridge to allow the VM to access the hardware.
To note, this is why it's important for VMs to be running with the latest IC version.