In an AdvancedDisk configuration the disk volumes can be created from individual LUNs using a logical volume manager such as VxVM to create volumes of any size. When creating disk volumes for use in an AdvancedDisk Disk Pool there are two factors to consider for optimal performance:
1. To avoid backups spanning multiple volumes the size of each disk volume should be larger than the largest backup that will be written to it.
I don't think there is a upper limit of disk space Netbackup can handle. Is more a qustion of what the OS supports.
From Wikipedia: http://en.wikipedia.org/wiki/NTFS