Updating the software of the Hardware Appliance always requires a reboot. Restarting the Hardware Appliance in a cluster should always be planned carefully to avoid inadvertently affecting the performance of the cluster. It is a common mistake to neglect operational caution when it is known that there are technical measures to intercept errors and thus give away security reserves. In a cluster, the software update should be applied on a single node at a time. Only if the node you are currently working on is complete and it has been confirmed that it is operational again, should you proceed to update the next node.
We recommend starting the update process with node three, as you will still be able to restore a cluster from node 1 in case of an emergency.
The Hardware Appliance firmware should be updated separately from the applications installed. To upgrade both, the firmware and the application, start with the firmware.
Software update on a three-node cluster
To update a three-node cluster, do the following:
- Before starting any configuration changes on a cluster node, confirm that the node has been running fine up to now. This is the only way to know for sure whether you actually broke anything if the procedure does not succeed as expected.
- You might also want to make a last manual backup of the Hardware Appliance
- Make sure this cluster node is declared as not operational, (e.g. disabling in load balancing frontend), so that:
- No other operator does any maintenance on any other node while we deliberately reduce redundancy on the cluster.
- Nobody relies on the availability of this node during maintenance downtime.
- No alarm is triggered if this node is no longer available.
- Start the software update procedure on node three by updating the Hardware Appliance firmware first, then updating the COS applications. This should generally be the same procedure as described in the Platform section: Install firmware, reboot, install application.
- After the cluster node has been rebooted, check that the node is operating correctly.
- After you asserted that this node is up and running, verify that the entire cluster is in good shape, i.e. that all of the cluster nodes of your cluster confirm that your cluster is back up and running with redundancy.
- Announce this cluster node to be operational back again or whatever you need to undo from step 3.
- Continue with updating your cluster by applying the same steps on the next cluster node, restarting at step 1.
Software update on a two-node cluster
To update a two-node cluster, follow the procedure described for three-node cluster, starting on node two.
