NetApp FC4600 Hardware Cabling Manual page 33

NOTE When you mix different types of drive trays, you must consider the total
number of drives that are available in the final configuration of the storage array. For
example, if you mix FC4600 drive trays with FC2610 drive trays, the total number of
drivedrives might be more than the maximum number that each drive channel can
support.
Figure 7 Suitable cabling topologies for Multiple SBOD Drive Trays
Chapter 1: Cabling Concepts and Best Practices 23