QEMU KVM Libvirt手册(10): KVM的各种限制

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　　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 .
  

　　MAC addresses

• 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

• 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.
  

　　User Permissions

• The management tools (Virtual Machine Manager, virsh, vm-install) need to authenticate with libvirt
  

　　Suspending/Hibernating the VM Host Server

• Suspending or hibernating the VM Host Server system while guests are running is not supported.
  

　　Performance