what a "real life application workload" looks like is entirely dependent on your use case, but fio is very widely used in the storage industry

it's a good first approximation to test the cartesian product of

- sequential/random

- reads/writes

- in arbitrary sizes

- with arbitrarily many workers

- with many different backends to perform such i/o including io_uring

and its reporting is solid and thorough

implementing the same for your specific workload is often not trivial at all