Backup of large virtual machines

Hello,

If possible I need your feedback about this, I am using Netbackup 7.5.0.6.

I have a VM of 2 TB. The full size of the VM backup is almost the same size, but the cumulative incremental backups are 1.3 TB size (more or less) and I have problems to duplicate it to tape (because of time).

I don't have much experience with Netbackup, so my doubts are:

1. The incremental backup size sounds fine? I mean if another person on the community have similar scenarios an the backup is smaller?.
2. Enabling CBT on the VM properties, is a good option?

Thanks in advance,

Jorge