How many KVM make sense to run ? (Proxmox) [duplicate]

Solution 1:

In general the larger the hypervisors and the more diverse the work load, the more you can overcommit assigning resources to customers/VM's.

On most hypervisors you can't really overcommit memory all that much, because things will fall apart somewhat catastrophically when all VM's want to actually utilise their assigned memory at the same time. That means that on a physical server with 32 GB of RAM you can reliably host ± 16 VM's which each are assigned 2 GB of RAM or two VM's when each is assigned 16GB. Basic math. Maybe more if you have a much better idea of your average and peak work loads.

It really depends on your CPU load if overcommitting CPU makes sense. With 16 cores available in the hypervisor you can create 16 VM's with each 1 VCPU or two with 8 VCPU's each and be sure that there will almost never be any resource contention. Again the math is elementary.
But when average the CPU load of each VPS is lower and their peak loads don't coincide, you can assign all of them two VCPU's (an overcommit ratio of 2) and that might still work out for you.

Note that if you want to create your own hosting platform in addition to hypervisors you generally also need a better management solution than just a collection of pets, as well a network and storage capacity.