HP StorageWorks HSG80 ACS Solution Software V8.8 for Sun Solaris Installation and Configuration Guide (AA-RV1RA-TE, March 2005)

FC Configuration Procedures
160 HSG80 ACS Solution Software V8.8 for Sun Solaris Installation and Configuration Guide
When speaking of a single controller, it is correct to say Active-Passive as that
describes the state of the channels. This is shown with a single controller in
Table 17.
When applied to the controller pair, both controllers are active, and the correct
designation is Active-Active.
Hubs
Hubs serve to create the connections within a loop. They also contain port-bypass
circuitry to allow malfunctioning nodes to be bypassed, thus enabling the loop to
continue to function.
Note: Because cascading hubs are not supported, the largest supported loop
configuration using hubs consists of 12 ports maximum.
Switches
Switches enable multiple connections to each other. With switches, the Fibre
Channel is removed from some of the limitations of an arbitrated loop, such as
throughput, single point of failure, and sizing of configuration.
In Case 2, both I/O channels are protected as well as distributing the processing
load over both controllers.
The fact that one controller is active while the other controller is passive leads to a
misnomer of Active-Passive to describe the redundant pair. The reason that this is
a misnomer is the fact that the description is referring to a single controller and not
the controller pair.
Table 16: Case 2: Active-Active (Describes the controller pair)
Channel 1 - Active Channel 2 -
Passive
Controller A Primary Ch 1,
Standby Ch 2
Channel 1 -
Passive
Channel 2 - Active Controller B Primary Ch 1,
Standby Ch 2
Table 17: Example of Active-Passive with a Single Controller
Channel 1 - Active Channel 2 -
Passive
Controller A Primary Ch 1,
Standby Ch 2