Accelerated life tests and software aging
Accelerated life test (ALT) methods are successfully applied in many industries to reduce the test period of highly dependable products. Software industry is not different, having the same demand to reduce the period of test for software products with very low failure rates. Since software is now part of many important processes of modern life, increasingly software-based products are expected to be highly dependable, which requires sophisticated techniques to test them within acceptable time frames. The use of ALT assumes that the system under test has its life reduced when it is exposed to some stress load. Many software products show a systematic performability and dependability degradation under certain circumstances, mainly when varying workload and long execution time are present. These software system degradations have been investigated over the last decade and now they are well explained through the software aging theory. In this chapter, we discuss how to apply accelerated life test techniques to software systems that suffer from software aging. We show how the software aging theory enables the usage of ALT methods to estimate the time to failure of a software system. We show a real case study, related to a widely adopted web server software system, to illustrate how to systematically apply ALT in software experimental studies. In this experimental study, ALT offers a reduction of approximately seven times the time required to obtain the same amount of failure data in use condition (without acceleration).
