High availability problems

In an HA pair, there can only be one primary node providing messaging operations. If the member acting as a primary detects that the other server is acting as a primary, it results in a split brain condition.

Split brain

When the HA pair detects it is in a split brain situation, both nodes are put into maintenance mode, and the administrator must select which member to operate as the primary and the standby nodes. Split brain situations are infrequent. You might see a split brain situation after simultaneous outages of both the primary and standby when they are both restarted. An interruption of the network interfaces between two operation appliances, such as disconnecting the cable, can also result in a split brain situation.

Identify which appliance is to be primary, and which appliance is to be standby.

Clean the store of the standby appliance. Type the following commands:

imaserver runmode maintenance
imaserver stop
imaserver start
imaserver runmode clean_store
imaserver stop
imaserver start

Stop the standby appliance and then stop the primary appliance by typing the following at each console:
```
imaserver stop
```
Start the standby appliance by typing:
```
imaserver start
```
This will cause it to run in maintenance mode.
Set the standby appliance to run in production mode by typing:
```
imaserver runmode production
```
Start the primary appliance and then the standby appliance by typing at each console:
```
imaserver start
```