Migrating a Virtual Machine from ESX Server 2.1 to 2.0.1 Might Degrade Performance (1484)
ESX Server 2.1 does not require that the idler service be installed in its virtual machines. Furthermore, the idler service is automatically uninstalled when the ESX Server 2.1 tools are installed in a virtual machine. ESX Server 2.0.1, on the other hand, does require that the idler service be installed in its virtual machines.
If a virtual machine is migrated with VMotion from ESX Server 2.1 to ESX Server 2.0.1, the idler service may not be installed. This may result in adverse performance of the virtual machine on the ESX Server 2.0.1 machine.
Migrating with VMotion a virtual machine from an ESX Server 2.0.1 to an ESX Server 2.1 is not recommended.