Assume that the same two components described in Two-Unit Series System are placed in parallel.

In this case, the reliability curve is as shown below.

Note the different shape of this curve. It does not have an exponentially decaying shape like the curve in the series system, and its hazard rate function is not constant.

This means that even if all items in a system follow constant failure rates, the system itself does not necessarily have constant failure rate. One of the reasons for this phenomenon is that redundancy in a system causes fewer failures to occur early in the lifetime of a system.