An administrator configures storage units STU-A and STU-B into a storage unit group in Failover mode.
If STU-A is busy, what does STU-B do?
A. queue remaining jobs and wait for STU-A to become available
B. write backups to tape if disk staging is enabled
C. fail over and write backups to STU-B
D. fail the job with a status code 219: Required storage unit is unavailable