CompTIA Server+ SK0-005 Practice Question
During a disaster-recovery drill, you attempt to restore Friday night's differential backup of a virtualized file server from a disk-based repository. The restore wizard aborts almost immediately and displays the message "Required base image not found."
The established backup policy dictates a weekly full backup each Saturday at 22:00, nightly differential backups from Sunday through Friday at 22:00, and a seven-day retention period. The job report for the last Saturday full backup shows the warning "Write operation failed - repository out of space; job finished with warnings." No errors were reported for the subsequent differential jobs.
Which of the following is the most likely root cause of the restore failure?
Changed-block tracking was reset after a host firmware update, so the differential file no longer matches the CBT map.
The backup catalog index for the job exceeded its retention period and must be rebuilt before restores can succeed.
The repository ran out of space during the last full backup, leaving that backup incomplete and breaking the differential chain.
The differential set was encrypted with a different passphrase than the most recent full backup.