Error injection aimed at fault removal in fault tolerance mechanisms-criteria for error selection using field data on software faults

Fault injection allows a detailed study of complex interactions between faults and fault handling mechanisms. It can be a useful complement to analytical modeling and formal verification techniques in the testing of fault tolerant systems. However, work on fault injection has not matured adequately to provide industry with cost effective alternatives for the validation of fault tolerant systems. This study analyzes 408 customer discovered faults (defects) in a release of a large operating system product. We discuss methods to select the error types for an error injection experiment in the system test environment, aimed at fault removal. Using four levels of severity and a total of 24 error types as recorded in the customer defects records, we analyze the faults in terms of fault types and system test triggers as defined in ODC. Our work shows examples of criteria that can be used to select errors for injection that use the information from the field reported defects.