Staging backups is the process in which a backup is written to a storage unit, then duplicated to a second storage unit. Eligible backups are deleted on the initial storage unit when space is needed for more backups.
This two-stage process allows a NetBackup environment to leverage the advantages of disk-based backups for recovery in the short term.
More Information
Disk staging storage unit size and capacity
Finding potential free space on a BasicDisk disk staging storage unit
About the Disk Staging Schedule dialog box