Backing up big data through NDMP

Hi Guys,

We have volume size of 42TB data to be backup with local NDMP backup going to tape library, it is taking more than 20 days to complete, luckly we don't have much network issues.

I was wondering if some one suggest me having succesful backup in minimum time? any other methods?

Netbackup master: 7.1.0.3

Media: 7.1.0.3

Netapp filer: Ontap 8.1.2P2

I am taking backup using snapshot ex: /vol/TP_MYDOCS/.snapshot/weekly.0

We have snap mirror configured from Production to DR filer and NDMP backups are being taken from DR filer.

Please let me know if any aditional details.

Thank you so much in advance.

Sagar