Dell PowerVault MD3200 Owner's Manual page 250

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 are done
d
(for example, the IP addresses are 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
may not have access to the storage array. A new version of MDSM may be
needed to manage the storage array with the new version of the controller
firmware.
If this problem exists, see 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 are 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 may exist with the
controllers.
If these problems exist, see support.dell.com.
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Troubleshooting: Your Storage Array Software