Dell PowerVault MD3220 Owner's Manual page 238

Examine the ethernet cables to make sure that you cannot see any
c
damage and that they are tightly connected.
Make sure that the applicable network configuration tasks have been
d
done (for example, the IP addresses have been assigned to each
controller).
5 Make sure that the controller firmware is compatible with MDSM on your
management station. If the controller firmware was upgraded, the MDSM
might not have access to the storage array. A new version of MDSM might
be needed to manage the storage array with the new version of the
controller firmware.
If this problem exists, see the Dell support website at support.dell.com.
6 Look to see if there is too much network traffic to one or more controllers.
This problem corrects itself because the MDSM tries to re-establish
communication with the controllers in the storage array at regular times. If
the storage array was unresponsive and a subsequent try to connect to the
storage array succeeds, the storage array becomes responsive.
7 For an out-of-band storage array, look to see if management operations are
taking place on the storage array from other storage management stations.
The type of management operations being done and the number of
management sessions taking place together establish the number of
TCP/IP connections made to a controller. When the maximum number of
TCP/IP connections have been made, the controller stops responding.
This problem corrects itself because after some TCP/IP connections
complete, the controller then becomes responsive to other connection
tries.
8 If the storage array is still unresponsive, problems might exist with the
controllers.
If these problems exist, see the Dell support website at support.dell.com.
238
Troubleshooting: Your Storage Array Software