Accusys ExaRAID GUI - Manual (Page 203)

Advanced Functions
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5.3.4 Controller and Path Failover/Failback Scenarios
By incorporating with the MPIO driver, the access to any virtual disk can
be continued when one of the controller is failed. Two principles should
be cared for proper operation:
1. MPIO driver must be installed in the hosts.
2. All virtual disks must be mapped to the host across two controllers.
Path Failover Across Controllers
The paths to a VD on its preferred controller are called active paths, while
the paths on the counterpart are called standby paths. When all active
paths are failed, the MPIO driver directs the traffic to standby paths.
Figure 5-11 depicts the scenario.
Path Failback Across Controllers
When any active path is restored, the MPIO driver routes the traffic back
to the active path automatically. No user intervention is needed for the
path failback process.
Add WWPN of HBAs to hosts HBA0 WWPN -> Host 0 -> Host Group 0
HBA1 WWPN -> Host 1 -> Host Group 0
Map LUNs to host groups DG0LD0 and DG1LD0 -> Host Group 0
Note
The path failure may be caused by pure path failure or controller
failure.
DG0LD0
DG1LD0
Host Group 0
DG0LD0
DG1LD0
Host Group 0
Host
Controller B Controller A
Host
Controller B Controller A
Figure 5-11 Controller failover