When implementing a differential backup strategy, what happens if the last full backup is lost?

• A. All differential backups made afterwards are also lost
• B. Restoration cannot be performed until another full backup is taken
• C. Only data from the last differential backup can be restored
• D. Data can still be restored from the last full backup

Answer: (B)

When utilizing a differential backup strategy, the approach hinges on the relationship between full backups and the differential backups created thereafter. A differential backup captures only the data changes made since the last full backup. If the last full backup is lost, it fundamentally compromises the entire differential backup chain because every differential backup is dependent on that full backup.

In this context, if the last full backup is no longer available, restoration of the data cannot be completed until a new full backup is taken. This new full backup is essential as it establishes the base state from which subsequent differential backups can capture changes. Without a valid reference point of the complete dataset—the lost full backup—the differential backups cannot be accurately restored, leading to the conclusion that restoration is not possible until a new full backup is created.

This highlights the critical importance of full backups in any backup strategy, as they serve as the necessary foundation for differential and incremental backups.