We're a Scrum shop and our consultant says CMMI requires us to have a measurement book for every project and every process area that proves we are performing GP2.8. This is too much overhead and doesn't seem useful. Can you help?
Danger Will Robinson! Danger! Fire your consultant immediately! Any time you hear the phrase "The CMMI requires ....." you should be wary. The CMMI requires only a few things, the vast majority of it are guidelines to be interpreted within your organizational context.
Don't forget to embrace self-organization and collaboration on this subject.
I agree with you that a process metrics "book" for each project makes no sense in your context. It directly conflicts with the essence of Scrum (or any other agile approach) and probably would add little value, if any.
One of the things that is interesting about agile organizations is that when it comes to "process" they typically have a "waterfall" mentality. This brute-force method to satisfying the CMMI doesn't help us get any better . . . kinda the point of the whole thing.
I would advise you to embrace agility, team collaboration, and self-organization to solve this problem, in other words, be agile!
It helps me to ask the question "why is this practice in the CMMI model?" GP2.8 is there to help us understand if the process is working for us, and to use that data as a basis for improvement. One method you might consider is to survey the team on each of the relevant processes at different points in the project and get THEIR feedback on how well they think things like managing the backlog, prioritizing, using story points, refactoring, etc worked and how they might improve those things. Doing this during the retrospective, and focusing on a comprehensive list of processes (as opposed to just talking), would give you some good data about what is working, what isn't, and how to make it better.
Better yet, if your record the results of the team survey so that management and scrum masters can look at aggregate trends, then you would really have some good data for continuous improvement.
This type of self-organization provides more value than a metrics book can.
CMMI, agility, Scrum, process monitoring . . . Bam! Not as hard as it sounds.