Patent ID: 7669073
Filing Date: 2010-02-23
Classification: G06F

Abstract:
1. A method for splitting a fault-tolerant computer system comprising at least two processing subsystems executing in lockstep, wherein each processing subsystem executes identical instructions substantially simultaneously, the method comprising: designating an active subsystem and an upgrade subsystem from among the at least two processing subsystems, the active subsystem comprising a first processor and the upgrade subsystem comprising a second processor; isolating components within the upgrade subsystem from the other subsystems; splitting the fault-tolerant computer system after designating the active subsystem and the upgrade subsystem such that, at the time of the split, the first processor of the active subsystem and the second processor of the upgrade subsystem have identical operational states, but thereafter operate independently for the duration of a software upgrade and cease lockstep operation during the software upgrade; and after the software upgrade, resuming lockstep operation.