Have you seen this for 7.6 release notes?

Non-NTFS thin disk VMs get restored as thick disk during disaster recover
NW127446
When NetWorker backs up a non-NTFS thin disk VM, both allocated sectors and
unallocated sectors get backed up. As a result, upon disaster recovery of the 
thin
disk VM, the thin disk is fully allocated, and is restored as thick disk.

You'll have to look up if there is a fix for this yet or not, if it applies to 
you?

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