Create a Contingency Plan
In addition to your implementation plan, consider creating a contingency plan. Building a cluster is a complex, time-consuming process and is not always free from complication. If your cluster implementation is the first set of hardware/software in your network, then a contingency plan may not be required, but if you are attempting to integrate your cluster system with an existing network, a contingency plan is a must.
The contingency plan is similar to the implementation plan, but rather than building a plan to install a system, it is constructed to give engineers a "way out." Contingency planning allows you to plan the reverse of the implementation so that you can roll back the changes that you have made in the case of a failure that prevents users from accessing the network or some other vital network task. This can be advantageous when you are operating in an environment with minimal tolerance for downtime.
Although contingency planning sounds simple, it isn't. You can't just reverse the process that implemented your system (although that may work in some cases.) To create a contingency plan, you must review the impact of each change you will be making as detailed in your implementation plan. Some changes can be easily reversed, but some changes are irreversible. Your best bet in building a contingency plan is to assume you have completed the installation of the cluster and it fails to function properly. What steps do you need to take to restore network services to the clients? You may find that you have not changed anything that affects the clients, but in the event you have, those changes will need to be reversed as part of your contingency plan.