NBU version?
Normal client with disk failure?
System (O/S) disk or data disk?
Here is a link to NBU 6.5 Troubleshooting Guide:
ftp://exftpp.symantec.com/pub/support/products/NetBackup_Enterprise_Server/348472.pdf
Chapter 7 - Disaster Recovery
p.525:
Disk recovery procedures for UNIX
The following section describes the procedures for three different types of disk recovery for UNIX:
■ Master server disk recovery procedures
■ Media server disk recovery procedures
■ Client disk recovery procedures