Overcommits
- KVM allows for both memory and disk space overcommit.
- However, hard errors resulting from exceeding available resources will result in guest failures.
- CPU overcommit is also supported but carries performance implications.
Time Synchronization
kvm-clock- NTP or similar network based time keeping protocols are also highly recommended (for VM Host Server and VM Guest) to help maintain a stable time.
- Running NTP inside the guest is not recommended when using the
kvm-clock.
- If no MAC address is specified for a NIC, a default MAC address will be assigned.
- This may result in network problems when more than one NIC receives the same MAC address.
- It is recommended to always assure a unique MAC address has been assigned for each NIC.
- Live Migration is only possible between VM Host Servers with the same CPU features and no physical devices passed from host to guest.
- Guest storage has to be accessible from both VM Host Servers and guest definitions need to be compatible.
- VM Host Server and VM Guests need to have proper timekeeping installed.
- The management tools (Virtual Machine Manager, virsh, vm-install) need to authenticate with
libvirt
- Suspending or hibernating the VM Host Server system while guests are running is not supported.
Performance
