A method for upgrading programs while they are running, without reducing fault-tolerance

摘要

When updating a running program in a system that uses a one-to-one backup program, fault-tolerance is lost while the backup program is itself being updated. To overcome this temporary loss of an available backup program, the number of backup copies of a software process is temporarily and dynamically increased during the software upgrade. The extra backup software processes may run on an unused processing unit or may run as an extra software process on a processing unit which is already performing a task. The technique may be applied to communication line cards.