Dell PS4100 Technical Information download pdf (Page 12)

June 2012 Dell EqualLogic Configuration Guide v13.2 6

prevent volume connections between hosts and SAN from being dropped in the event of an active

controller failure.

The

Active Controller

is the controller which is processing all disk and network I/O operations for the

array. A second controller in dual controller configurations will always be in a “passive” operating

mode. In this mode, the secondary controller will exhibit the following characteristics:

• Each of its Ethernet ports are electrically inactive (active lights are off)

• The passive controller cache mirrors the cache of the active controller.

2.3.3 Controller Failover behavior in all models prior to PS4100/PS6100

To support redundant controller fail over, each Ethernet port on the active controller that is connected

to the SAN must have its corresponding port on the passive controller also connected to the same

SAN network. In the event of a controller failure, the passive controller will immediately activate and

continue to process all data requests to the array. The following changes occur during fail over:

• The backup controller automatically enables each of the corresponding Ethernet ports that

were enabled on the failed primary controller

• The IP addresses that were assigned to each of the failed controller Ethernet ports are

reassigned to the corresponding ports on the second controller.

A link failure on one or more of the Ethernet ports on the active controller does not constitute a

controller failure. For this reason, 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.

It is also critical that port connections for both controllers are configured so that the

corresponding

ports on each controller are connected to the SAN

. If port 0 on the active controller is the only port

connected to the SAN, then you must use port 0 on the passive controller for the other connection to

the SAN. This is illustrated in the partially connected scenario shown in Figure 1.

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Dell PS4100 Technical Information Page 12