Switch upgrade causes messages to drop (4275571)

After upgrading the software on the switches servicing an SSB node communications between the node dropped and as a result the data link between the primary & secondary nodes also dropped. When the upgrade was finished the communication between the switch and the secondary node was not re-established. In order to re-establish proper communications, the SSB needed to be rebooted.

The following procedure is advised when upgrading the software on switches that an SSB nodes are connected to in order to prevent log loss.

1. Shutdown the secondary node
2. Upgrade the switch associated with the secondary node.
3. Once the upgrade is complete reboot the secondary node.
4. Fail over to the secondary node.
5. Shutdown what was the primary node (now the secondary)
6. Upgrade the switch
7. Reboot the node
8. Fail back to the original primary.

This should ensure that there is always one node online and there is no interruption to the flow of logs during the upgrade.