Failure rate of parallel systems

[thiravia]

I know that the failure rates are additive in a series system. What happens to the failure rate of a parallel system ? Is there a simple way to calculate it ? (assuming constant failure rate of individual components.)

I know that I can find the reliability of the system , from the reliability of the individual components , and then back calculuate the system failure rate. Is there are better easier way ? ?

[Pantelis]

See http://www.reliasoftforums.com/showthread.php?t=2435

[leomartin6]

In a simple parallel system, at least one of the units must succeed for the system to succeed. Units in parallel are also referred to as redundant units. Redundancy is a very important aspect of system design and reliability in that adding redundancy is one of several methods of improving system reliability. It is widely used in the aerospace industry and generally used in mission critical systems. Other example applications include the RAID computer hard drive systems, brake systems and support cables in bridges.
The probability of failure, or unreliability, for a system with n statistically independent parallel components is the probability that unit 1 fails and unit 2 fails and all of the other units in the system fail. So in a parallel system, all n units must fail for the system to fail. Put another way, if unit 1 succeeds or unit 2 succeeds or any of the n units succeeds, then the system succeeds.