D-Link DSN-6020 User Manual page 146

Step 4
Power off the DSN-6410. Insert the second controller to the IP SAN storage. And then
power on the system. The IP SAN storage should now become in dual controller mode as
the DSN-6410 with DSN-640.
You may go to "Maintenance\System information" to check out. The IP SAN storage is
running in dual controller mode now.
146