Which KVM virtualization system to choose?

Question

KVM

Quite a few have passed since the last question on this topic ( https://toster.ru/q/121071) , especially since the question is generalized.
At the moment, we are choosing a serious KVM product, there are the following options:
1) ProxMox
2) OpenNebula
3) OpenStack
As a result, we get:
ProxMox
We have already practically rolled back the ProxMox solution, we got a cluster on it and got DRBD + Fencing.
In principle, it works, almost everything suits, except for the backup system.
OpenNebula Have
n't tried it yet but read enough documentation.
They didn’t quite understand how fault tolerance is provided on OpenNebula, give a link to a digestible description / manul, point to the right path))
Interested in practical experience, who raised the cluster and fault-tolerant system on it? How is the backup system implemented?
OpenStack
This monster finally scares))) Of course, it fits, but everyone scares him with his settings. Is it worth bothering for 3 servers and about 20 virtual machines?
Thanks for sharing your knowledge!

Answer 1

what is open stack what is open nebula in the context of three servers in general past
here it was necessary to choose something like
esxi
xen server
native kvm
proxmox
In your case it is obvious that proxmox is the easiest

Answer 2

Proxmox, what's the disadvantage of backing it up?
and complexity of administration?

Answer 3

oVirt or if there is a budget - RHEV. In general, it seems to be written that the choice is serious, but the description of the question is absolutely frivolous. You need to start with the requirements for the system: scale and scalability (there is a difference between 10 hosts and 10,000, isn’t there?), Types of load, planned hardware, not only hosts, but also storage and network infrastructure, specific requirements for features, criticality of the system (how many stands idle), etc.