When performing a backup of a virtual machine where thin provisioning is used, one of the steps is to query vSphere to find out which blocks are in use. Once a virtual machine has written to a block o...When performing a backup of a virtual machine where thin provisioning is used, one of the steps is to query vSphere to find out which blocks are in use. Once a virtual machine has written to a block on virtual disk, the block is considered in use. So, it will perform the backup of vmdk's located on non-VMFS datastores like for example NFS, the full provisioned size of the thin disks will be sent to the server.