For a redundant (array) system, he (or she) who considers that the total system reliability might be worse than a non-redundant system because of additional circuits' faults might naturally say, "Is the redundancy really use full?". The main purpose of this paper is to answer the question for redundant array systems using E-1? track switch [1] and a reconfiguration method [2]. The answer is "the redundancy using these methods is useful!". Furthermore, the condition that the assumption that additional circuits such as tracks, switches, etc. Are fault-free becomes valid is given.