The NetBackup 10.1 admin guide  says about the "Exclude deleted blocks" VMware optimizations:
Reduces the size of the backup image by excluding any unused or deleted blocks within the file system on the virtual machine. This option supports the following file systems: Windows NTFS, and Linux ext2, ext3, and ext4.
This option uses proprietary mapping technology to identify vacant sectors (allocated but empty) within the file system.
Currently all our RHEL based virtual machines are using XFS filesystem, which is the default by Red Hat. Is this feature likely to come for XFS or is it worth to change our templates to use ext4 filesystem instead?