Diagnose "Storage Performance" messures the Speed of the selected Storage.
The storage device for testing can be either a single storage or ALL, the selection can be updated with "Update selftest Parameter".
Tresholds can be set in kb/sec for warnings and errors.
To better understand how slow the not recommended CIFS protocol is (compared to other protocols) , especially when working with small files, the block size parameter can be used.
You will see a huge difference between 1kb (representing small files) and 1mb block size.