Hello. I'll pose the question first and then provide a brief overview of our environment.
What is VMware's recommended VM density (or best practice)? I realize that that's a loaded question, but let's assume that most of our VMs are Windows Server 2016 or 2019 with 2 vCPUs, 2 cores per CPU (4 cores total) and 8GB of RAM. The storage back end is a 10GbE iSCSI connected SAN.
Environmental's
4 Dell PowerEdge R730xd
Storage
At one point in my career, the VM per host density was right around 20, but not sure if that changed.
Be well.
This really is one of it depends on answers. If you have 40 cores and 20 2 core machines always at 100 percent you can only do 20 machines, but if you have 100 machines at 20 percent all the time you can get away with a 5:1. Thats why desktops generally can do 5:1 but a general metric I've seen for servers is 4:1 or 2:1.
Thank you sjesse. I appreciate the feedback.
So, if we have 2 CPUs (sockets), each 12 cores, this would give us 24 cores. According to vSphere, I have 48 logical processors, I'm assuming because of hyperthreading. Most of our VMs are running at roughly 20%. When you give the 4:1 ratio, is that per host or per CPU (core). Assuming per host as that was my original ask, but just wanted to clarify.
You need to remember that at 100% cpu usage a logical processor is 50% of the physical, while hyperthreading helps a bit, I'd only look at physical cores. If you really want to be safe once you get a number where you feel comfortable and you can't take a performance hit you also need to consider what happens if a host fails.