Both fault-tolerant components and redundant components tend to increase cost.

Typically disk arrays increase level of availability by using redundant components other than RAID, such as power supplies.

Strategies for the avoidance of common mode failures include keeping redundant components physically isolated.

More expensive servers will have redundant components, so that if one fails another will take over automatically.

Fault tolerance uses redundant components to allow the computer to continue operating even when a part fails.

Redundant items do not contribute to availability reduction unless all of the redundant components fail simultaneously.

Redundancy works best when the redundant components are truly independent.

And since each added redundant component adds to the chance of a component failure, a system's reliability can seem worse even as it approaches perfection.

Each connection required redundant components, multiple terminations, and countless shunts and conductors.

It is necessary to know how often different parts of the system are going to fail even for redundant components.