Technical information

48 EqualLogic Configuration Guide | Version 15.2 | August 2014
We illustrate controller failover behavior for the PS4100 family controller in Figure 11. Controller failover
behavior for the PS6100 (4 port) controller family is identical.
Note: 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 11.
Figure 11 Controller failover process and optimal connection paths
9.4.3 Failover behavior in the PS-M4110
Each PS-M4110 array is configured with dual controllers, active and passive connections, and
redundant fabrics to provide redundancy and prevent volume connections between hosts and SAN from
being dropped in the event of a failure.
There are three failure scenarios that are protected by the array:
 In the event of a link failure, the active link of the active port goes down, and the standby
link for the same port takes over.
 In the event of a switch failure, both active and passive ports automatically link to the
redundant fabric switch.
 If the active controller fails, the passive controller takes over.