US Patent 7210071 Fault tracing in systems with virtualization layers

In a stacked system, errors detected at a user application interface of one or more host systems are associated with root cause errors at a stack level below a virtualization layer by detecting an error at a user application interface; identifying an associated root cause error at a lower stack level; creating an error trace entry for the error; associating an error log identifier with the error trace entry; making the combined error log identifier and the error trace entry into an error identifier that is unique within the plurality of host systems in said stacked system; and communicating the error identifier to any requester of a service at a user application interface of one or more host systems when the service must be failed because of the root cause error.