VM density per ESXi host

[MAThompsPCSO]

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

• 2x Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz (2 sockets, 12 cores per socket, 48 logical processors)
• 384GB RAM
• 1Gbps VM network (2x 1Gbps ports)

Storage

• Nimble CS300 array
• 10Gb optical

At one point in my career, the VM per host density was right around 20, but not sure if that changed.

Be well.

[sjesse]

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. 

[MAThompsPCSO]

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.

[sjesse]

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.