System information

Advanced Functions
5-20
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.
• Controller Failover and Failback Scenarios
When doing the controller failover and failback in the redundant-controller systems, the two controllers must meet the
following hardware and software requirements:
Hardware:
1. Both controllers are of the same model and PLD version
2. Same number and model of daughter boards installed on both controllers
3. Same BBM (battery backup module) number and state
4. Same memory size
Software:
Some software requirements can be updated synchronously during the controller failback. Users need to check and
confirm the pop-up message shown on the LCD panel so that the automatic synchronization can continue.
1. Same boot code
2. Same firmware version
3. Same BBM control options
4. Same enclosure serial number
Controller Failover
When one of two controllers is failed, the survival controller turns off the power of the failed one, taking over all
interrupted tasks. The host I/O is redirected to controller B by MPIO driver. Figure 5-12 shows the path switching while
controller failover.
Normally, the heartbeat LED on each controller board is flashing periodically and the system keeps syncing state
messages shown on the GUI to identify the controller is alive. When a heartbeat LED does not flash anymore, or the state
message cannot be synced, the controller will be regarded as failed.
Note
When the heartbeat LED of both controllers are flashing, users are allowed to hot remove any one
controller.
DG0LD0
DG1LD0
Host Group 0
DG0LD0
DG1LD0
Host Group 0
Host
Controller BController A
Host
Controller BController A
Figure 5-12 Controller failover scenario