Will SSD Speed Have a Greater Impact on the Host or Guest System?

Question

I am configuring a new Windows Server 2016 system and am planning to run several (3-5) Hyper-V virtual machines on it. I have two SSDs at my disposal - one fast, and one slow. I know it's best to put the host OS and the guest VMs on different drives, but which configuration will offer the best performance for the guest VMs? I read here that between a HDD and SSD, it's better to put the VMs on the SSD, but I'm not sure if that applies to two SSDs as the latency characteristics are different.

Answer 1

Apparently that depends which system the performance of you want to maximize. If you want to maximize guest systems' performance, then put them on the faster SSD. Virtualization doesn't demand as much resources on host system as normal tasks do. It's just basically processor instruction & memory address conversion. The host running on a slower drive won't impact guests' performance too much. What impacts guests' performance most is the virtualization technology of your CPU, Intel VT-d, VT-x or AMD-V.

Answer 2

Whatever your SSD speed is, it is unlikely that it is going to matter much, since it will hardly be the bottleneck in the performance of the guest OS. What matters more is the capacity and virtualization features of the processor you are using.

That said, if you are planning to perform any serious I/O inside the guest, then you should be putting it on the faster drive and vice versa. Wherever you are accessing more files from must be the faster drive. Another thing to do would be to keep your virtual memory on the faster SSD, just in case you have insufficient memory for virtualization.