This article applies to:

• Product edition: Phoenix 

Applicable scenarios

A thin disk is backed up or restored as a thick disk in the following scenarios:

• At the time of backup, CBT of the source VM was disabled. 
• Source VM resides on NFS datastore during backup.For NFS datastores, Phoenix cannot perform a * query to find the allocated data blocks.  Hence, the Phoenix VMware Agent does not detect the sparse block and backs up the sparse block as a zero data block. Therefore, the thin disk is converted into a thick disk during restore.
• At the time of backup, there was no sparse block present on the disk - Phoenix VMware agent does not change the disk type explicitly, but the change is from VMware when there is no sparse block on the disk of the restored VM.