When attempting a hot-add backup it fails with "Error Message: 3201 - can't open [DATASTORE] VM_NAME/VM_NAME.vmdk"
On this occasion, the cause of this behavior can be because hot-add backups are being attempted in a mixed mode cluster; e.g. ESXi 5.0, ESX 4.0 hosts being in same cluster
Configure the VMware ESX host cluster environment to have uniform versions of VMware ESX host(s) per cluster.
