Patent ID: 8943489
Filing Date: 2015-01-27
Classification: G06F

Abstract:
1. A method comprising: running a first primary virtual machine (VM) on a primary appliance of a network device, wherein the first primary VM executes a first operating system that controls functionality of the primary appliance; running a second primary VM on a secondary appliance of the network device, wherein the second primary VM on the secondary appliance executes the first operating system and provides high availability for the primary appliance; in response to receiving an in-service software upgrade (ISSU) request, initializing a first secondary VM on the primary appliance and a second secondary VM on the secondary appliance, wherein each of the first secondary VM and the second secondary VM execute the first operating system; performing the ISSU on the primary appliance by upgrading the first secondary VM on the primary appliance to a second operating system, switching control of the primary appliance from the first primary VM to the first secondary VM, and upgrading the first primary VM to the second operating system, wherein, during the ISSU of the primary appliance when the first primary VM and the first secondary VM on the primary appliance are executing different operating systems, the second primary VM executing the first operating system on the secondary appliance provides high availability for the primary appliance; and if the first primary VM on the primary appliance fails during the ISSU of the primary appliance when the first primary VM and the first secondary VM on the primary appliance are executing different operating systems, switching control of the functionality of the primary appliance from the first primary VM on the primary appliance to the second primary VM on the secondary appliance, wherein the second secondary VM on the secondary appliance provides high availability for the secondary appliance.