That was Then... This is Now

The reliability of a component is measured by the mean time between failures (MTBF). It is the average time until failure and is typically provided in hours or years. A MTBF of 10 years means that, on average, every 10 years a failure occurs, based on a large sample. These numbers are typically provided in the component data sheets of the hardware manufacturers. There are two problems associated with using the MTBF: 1. The values for MTBF can vary significantly, especially for components with moving parts like disk drives. This is because the MTBF depends greatly on the quality of the individual production batch which is far from constant. Manufacturers obviously try to detect quality problems, but this is not easy, as the manufacturing of complex components is more an art than a science. There are many variables, like calibration of machinery, impurities in the clean room, quality of materials, etc. 2. The appearance of failures does not follow a uniform distribution. The failur