Accusys ExaRAID GUI - Manual (Page 204)

Advanced Functions
5-31
• 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.
DG0LD0
DG1LD0
Host Group 0
DG0LD0
DG1LD0
Host Group 0
Host
Controller B Controller A
Host
Controller B Controller A
Figure 5-12 Controller failover scenario