So I'm familiar with how to get the size of a client via RSSPACECHECK or by running a test client copy; But when the system is using a database that utilizes columnar tables, like HANA, I have yet to find a good way to see how much space a client actually takes up.
For example, you have 3 clients. In each client's tables, there are unique values per column that exist in all clients. And since a columnar table only stores unique values once in each column, the size of all three columns is only the addition of difference between the clients plus the unique values (counted only once). So if you were to run the RSSPACECHECK report, it counts the expanded size of each client and the total of the three would add up to more than what HANA is actually storing.
I'm sure I could sit down and write up a query to figure this out but I wanted to see if anyone else has done this already? If not, I'll share once I have it figured out.