Technical information

June 2012 Dell EqualLogic Configuration Guide v13.2 10
2.3.6 Controller failover behavior: PS41x0/PS61x0
In the event of a controller failure the following changes occur:
• The passive controller immediately activates and continues to process all data requests to the
array.
• Vertical port pairing insures that IP addresses assigned to each of the failed controller Ethernet
ports apply to the corresponding ports on the second controller.
As stated in Section 2.3.3 above, controller models prior to the PS4100/PS6100 required having cabled
connections present on corresponding controller ports for controller failover to work correctly. The
vertical port failover feature in PS41x0/PS61x0 controllers eliminates this requirement, enabling
partially cabled configurations to support controller failover too. See Section 4.5.3,
Minimum Cabling
Scenarios: PS4100 and PS6100
, for details.
It is important to ensure that ports from each controller are connected to at least two different
switches. This will prevent a switch failure from also disabling all paths between a host and its
connected volumes. We illustrate controller failover behavior for the PS4100 family controller in Figure
3. Controller failover behavior for the PS6100 (4 port) controller family is identical.
IMPORTANT: To prevent a switch failure from also disabling all paths between a host and its
connected volumes, you should make sure that ports from each controller are connected to at
least two different switches. You should also split vertical port pair connections between two
switches to ensure 100% bandwidth capability is maintained in the event of a vertical port
failover event. Both of these guidelines are illustrated in Figure 3.
Figure 3 Controller Failover Process and Optimal Connection Paths