Cloning a Large Disk Seems to Occur Slowly (1391)
Cloning a large disk may take an excessive amount of time to complete.
Sharing a VMFS volume between ESX Server 2.0.1 and ESX Server 2.1.0 hosts slows down all SAN-related tasks for all servers on a shared LUN. This includes migration and migration with VMotion.
To speed up the process, ensure that the VMFS is not shared by multiple ESX Server 2.0.1 and ESX Server 2.1.0 hosts.
To correct upgrade to VirtualCenter 2.1 or later.