VMWare Diff and Cumulative Incrementals are very large

Hi all,

I am running 7.6.1.2 on Windows 2008.

I run a full backup of a VM and it backs up 37 Million files and 7.7TB in size. This job took about 60 hours (via SAN).

I than run a Cumulative and it runs a lot faster, backs up 154 thousand files and the job finishes in 3 hours (Using Accelarator) However, the size of the backup is 7.8 TB.

A differential is next and that backs up 25,180 files and only takes about 3 hours to finish. However, the size shows 7.8 TB.

See attached screenshot.

The number of files appears correct, but, why are the sizes of the actual backup so large? When duplicating to tape, Netbackup is duplicating the entire 7+ TB for a differencial (using SLP which backs up to dedupe disk first than tape)