I'm working through the official exam reference book for 70-764 by Isakov and some of the sample questions + answers are driving me crazy!
One such example is for a question which asks you to come up with a backup strategy to meet a set of requirements, one of these requirements being that the RTO is 15 minutes.
In the answer section for this question, the author states that an RTO of 15 minutes cannot be met by performing differential backups every 15 minutes but doesn't explain why this is the case. The author states that the correct answer is that log backups should be taken every 15 minutes instead. As far as i know, either of the two solutions could work, and you wouldn't be able to know this for sure until you tested how long it takes for the restore of the differential backups to complete.
Am i mistaken here?
Any help would be greatly appreciated!