The tool you are looking for is the Automated Workload Analyzer (AWA), and it's built into Data Ontap for both cDOT and 7-mode. The general process is that you start the tool, run some workloads, then stop and print the results (somewhat like a perfstat).
Data Ontap is already categorizing IO loads and collecting details about them. What AWA does is organize which IO loads would have been served via FlashCache or FlashPool as compared to the overall load. The summary output then identifies, based on the cache hit ratio desired, how much cache would be needed to get that ratio. If you already have some Flash (cache or pool) available, the AWA will also tell you how well the current Flash is doing for the workload being analyzed.
The AWA up to DoT 8.3 is aggregate based - that is a given aggregate is run through the process and the results are work against that aggregate. AWA in cDOT 8.3.1 will break that down to the volume level. Since you can tune how each volume is cached (random read/write versus sequential read/write in various combinations) the data allows you to finely tune which volumes in an aggregate make use of the various cache options (FlashCache/Pool) for instance as compared to others, thus making best use of your Flash even if the workloads aren't optimized per aggregate.
I've used the older AWA a lot to gather details which demonstrate what I have seen in other performance reports - my available cache is way undersized for my workloads. With recent deployment of cDOT 8.3.1 I'm looking forward to rerunning AWA collections to get volume level statistics ahead of budget planning to make sure I don't over buy where I don't need it.
More AWA information is available in the standard DOT documentation - not a hidden feature or anything like that. In "real" 7-mode back in the day I believe it was still present but a hidden or diagnostic access option only. Also - there are some bugs written against AWA that which are tied to filer disruption. I suggest using the support site to seach on "AWA" and verify that the conditions associated with those bugs don't apply to you or you are on a fixed version of DOT, just to be safe.
Hope this helps you.
Lead Storage Engineer
Huron Legal | Huron Consulting Group
NCIE - SAN, Data Protection