You cannot rename a Storage Unit in NetBackup (not in a supported way anyway!)
But is you mean just the storage unit and not the disk pool etc. then you can just delete the current one and then create a new one with the same attributes (screen shot it and look at it all carefully first) and then edit your policies / storage unit groups / SLPs etc. to use that one.
Of course always do a catalog backup first and make sure all SLP operations are up to date and nothing running before making such a change due to having to edit your SLPs
Hope this helps
