Hyper-V and Windows 10 Guest speed

What are the best memory settings for a Windows 10 Guest on Hyper-V?

16 Gb of physical memory

Bree said:

I just take the defaults offered when setting up a new virtual machine: 1024MB initial with dynamic memory enabled. On a 16GB machine the dynamic memory will allocate more memory to the VM as required, up to a maximum of 1048576MB by default (you may want to lower that upper limit to leave some for the host). These settings work very well with any Windows guest I've tried (XP, W7, W8 & W10).

If speed is your concern, then the hard drive is by far the more important factor. I have just migrated all my VM's from a machine with an HDD to one with an SSD. The two machines are similar specs apart from the hard drive but the difference in speed is dramatic. The VMs run as fast as if they were installed directly on the machine.

Re. SSD, totally the way to go.

Re. dynamic memory, I have found it can be temperamental, and prefer to use fixed RAM and initially set at 4 GB but you really need at least 8 GB RAM to do this. Dynamic is better if using multiple vms and limited RAM of course.

As allocated RAM, an equally important factor is the number of virtual processors (vCPU) you assign to a VM.

A good rule of thumb is to add 0.5 to 1 vCPU per VM per core on host CPU. Start testing VM performance with lower number of vCPU, for instance only one vCPU per four host cores, run the VM and check % Guest Run Time graph in Performance Monitor on host machine (not on VM). Shut down VM, increase the number of vCPU, run VM and check the graph again.

Screenshot shows how to add % Guest Run Time graph in Performance Monitor:



An example. A W10 PRO x64 version 1809 virtual machine using 4 GB static vRAM and two vCPU, running Windows Update. Hyper-V Manager shows its CPU usage fluctuates between 12% and 20%, and % Guest Run Time graph looks like this:



It's OK, you should only be worried about performance if the graph for a VM shows constant high values (over 75). Peeks can be up to 90, but if either the peek value often goes to over 90, or graph remains constantly close to 75, you need more vCPU.

Same VM, with 8 vCPU. Running WIndows Update on it looks much better, Hyper-V Manager shows CPU usage fluctuates between 1% and 3%, and the % Guest Run Time graph looks much better:



Virtual machine also feels "snappier" with 8 vCPU.

Kari

Kari said:

As allocated RAM, an equally important factor is the number of virtual processors (vCPU) you assign to a VM.

A good rule of thumb is to add 0.5 to 1 vCPU per VM per core on host CPU. Start testing VM performance with lower number of vCPU, for instance only one vCPU per four host cores, run the VM and check % Guest Run Time graph in Performance Monitor on host machine (not on VM). Shut down VM, increase the number of vCPU, run VM and check the graph again.

Screenshot shows how to add % Guest Run Time graph in Performance Monitor:



An example. A W10 PRO x64 version 1809 virtual machine using 4 GB static vRAM and two vCPU, running Windows Update. Hyper-V Manager shows its CPU usage fluctuates between 12% and 20%, and % Guest Run Time graph looks like this:



It's OK, you should only be worried about performance if the graph for a VM shows constant high values (over 75). Peeks can be up to 90, but if either the peek value often goes to over 90, or graph remains constantly close to 75, you need more vCPU.

Same VM, with 8 vCPU. Running WIndows Update on it looks much better, Hyper-V Manager shows CPU usage fluctuates between 1% and 3%, and the % Guest Run Time graph looks much better:



Virtual machine also feels "snappier" with 8 vCPU.

Kari

Set to 4 vCPUs. Running well.