As previously described, the nature of clustering can be quite complex. From experience, management often blindly demands full clustering without knowing and taking the full implications into account. Far too often, we hear something similar to this: "the system is mission critical, so it must be clustered". The common belief is that clustering will save the business and solve all issues that can be related to performance and availability. Now, clustering can and will help in many cases, but it is always important to be objective and help the management by explaining the actual needs and consequences, especially in terms of increased costs in maintenance and complexity.

It is important to always consider what kind of system is under discussion. For instance, a system that deals with upholding life, such as a "heart-lung machine", is a system that has to operate without errors every second it has a connected client (the patient). This scenario is, of course, extremely...