Vmware Block level backup question

[AlGon]

We'll soon be upgrading to Netbackup V7 and have already updated our VMware environment to Vsphere.  

I'm reading up on the new Netbakcup Vmware backup capabilites and im trying to understand how a block level incremental backup can actually reduce the backup size.

The manual says

Page 48 From the Netbackup Vmware Admin Guide

"This option reduces the size of full backups as well as the size of incremental backups, as follows."

I understand how this can increase speed but not how it can reduce the actual size of the backup compared to a normal incremental file level backup?  Is this an error in the documentation, or am I missing something?

Cheers

[Nicolai]

Have a look at this beak out  session from Vision 2010. There is a lot of talk about block level incremental backup. About 20 minutes from start.

https://www-secure.symantec.com/connect/videos/breakout-session-backing-virtual-machines-netbackup-7

[AlGon]

Good stuff Nicolai, a good video.  Will watch again later, thanks.

I'm still unsure how doing the incremental at block level reduces the size of the incremental backup :(