Which type of backup involves saving only changes made since the last backup?

The type of backup that involves saving only the changes made since the last backup is known as an incremental backup. This method is efficient in terms of storage space and speed, as it focuses solely on the new or altered data since the previous backup occurred.

For instance, if a full backup is taken on a Sunday, and incremental backups are conducted on Monday, Tuesday, and Wednesday, the backup taken on Monday will only include the changes made from Sunday to Monday, Tuesday's backup will reflect only changes from Monday to Tuesday, and so forth. This allows for quicker backup times and can significantly reduce the amount of data being stored, as only the new or modified information is saved.

In contrast, a full backup captures all data each time it is created, resulting in larger backup files. A differential backup saves changes made since the last full backup, which can grow larger over time until the next full backup is performed. A mirror backup creates an exact copy of the source data at a specific time, which means it can overwrite previous versions rather than saving only the changes. Understanding these distinctions is essential for designing efficient backup strategies in data management.