Optimal VM sizing (Scale out or Scale Up)

[kjoyce78]

Over the past few years, logic about applications has been to scale out horizontally rather than scale out vertically. Basically, spin up another node rather than add more resources to the vm. Traditionally I have used a 4 vCPU cap since my experience has told me most people jump right 8 vCPU for anything larger. Historically I have seen issues with too many 8 vCPU VMs causing issues with DRS and HA. Its generally easier to move around a ten 4 vCPU vms rather than five 8 vCPU vms. So my question to the community is, with all of the improvements in physical CPUs does that 4 vCPU still make sense?  Traditionally 1vCPU x 2GB = small 4 vCPU x 4GB = medium and a 8 vCPU x 16GB = large but with CPUs now having 28+ cores and all our hosts are dual processors, has a 8 vCPU VM now a medium? 

[admin]

Hi

many vCPU will cause CPU scheduling issue so that I wouldn't allocate a lot of vCPU if there is no clear reason.

below is from vsphere design course,

always start at 1vcpu. don't allocate many vcpu without clear reason.

with many physical core, you can allocate many vcpus but it doesn't mean it is good.

8vcpu VM is not medium, only a few application required such amount of vcpu and also you need to think about license cost due to increasing vCPU.