Limitations of Instant Clones

The instant clone feature provides good performance and scalability, but it has a few limitations:

• The instant clone feature is not available when you connect directly to ESXi. Instant clone depends on functionality available only in vCenter Server.
• Delta disks created during the instant clone operation are not visible in the snapshot trees of the virtual machines. They cannot be managed with the VirtualMachineSnapshot managed object. Instead, you must manage the delta disks using the VirtualMachine.Reconfigure() method.
• The instant clone operation is partly parallel and partly serialized. You can start several operations concurrently, but part of the process is exclusive and requires serialization of requests.
• The instant clone operation responds to errors by backing out changes, such as delta disks, to restore the previous state of the file system and the source virtual machine. However, there is a small window of failure at the end of the operation where the cloned virtual machine is independent and cannot be backed out to recover from an error. This is a low risk situation.
• Instant clones create a delta disk for both the source and generated virtual machine, so resources can run out after vSphere raises a warning. The source virtual machine may be frozen to avoid excess growth. For current limits and ways to deal with failures, see the KB article Instant Clone fails due to exceeding maximum number of delta disks.
• The instant clone operation does not allow you to specify a different host for the clone. The clone must be on the same host as the source virtual machine because they share memory and virtual disk files.