When should you ideally perform a differential backup?

Performing a differential backup is ideally done after the last full backup. This approach is effective because a differential backup captures all the changes made since the last full backup, allowing for a more efficient recovery process. When you conduct a full backup, it serves as the baseline for all future differential backups. Each subsequent differential backup stores only the changes made since that baseline full backup. This means that to restore data, you only need the last full backup and the most recent differential backup, streamlining the recovery process.

This method also minimizes storage space compared to conducting a full backup more frequently, as it only includes data changes rather than duplicating all existing data. It provides a balance between recovery time and backup space usage, making it an ideal choice for maintaining data integrity and ensuring quick recovery from data loss scenarios.

The other options do not align with the best practices for differential backups. Performing backups after every file change would be excessively frequent and resource-intensive. Scheduling a differential backup once a week without taking into account the timestamp of the last full backup does not capture all changes made since that backup. Lastly, performing them only when a full backup fails would mean that crucial data might not be adequately backed up during normal operations.