A company performs a full backup every Sunday at 02:00. Each night Monday through Saturday at 02:00, a second job backs up only files whose archive bit is still set and does not clear that bit when finished. Early Thursday morning a storage-array failure takes the file server offline. To recover the server with data current to the latest backup (Wednesday 02:00), which backup set(s) must the administrator restore?
The latest synthetic full backup automatically generated on Wednesday
Sunday's full backup and the Wednesday night backup only
Sunday's full backup, plus the Monday, Tuesday, and Wednesday night backups
The weekday job is a differential backup because it copies every file that has changed since the last full backup and leaves the archive bit unchanged. By design, restoring from a differential strategy requires just two backup sets: the most recent full backup and the most recent differential backup. Therefore, applying Sunday's full backup followed by the Wednesday night differential contains every change made up to that point. Incremental schedules would need the full plus each night's backup, while a synthetic full is created only when the software assembles one from existing sets-something not described in the scenario. Restoring only the Wednesday backup would miss unchanged files that exist only in the full set.