Architecture-Level Soft Error Analysis: Examining the Limits of Common Assumptions

This paper concerns the validity of a widely used method for estimating the architecture-level mean time to failure (
MTTF
) due to soft errors. The method first calculates the failure rate for an architecture-level component as the product of its raw error rate and an architecture vulnerability factor (
AVF
). Next, the method calculates the system failure rate as the sum of the failure rates (
SOFR
) of all components, and the system
MTTF
as the reciprocal of this failure rate. Both steps make significant assumptions. We investigate the validity of the
AVF+SOFR
method across a large design space, using both mathematical and experimental techniques with real program traces from
SPEC
2000 benchmarks and synthesized traces to simulate longer real-world workloads. We show that
AVF+SOFR
is valid for most of the realistic cases under current raw error rates. However, for some realistic combinations of large systems, long-running workloads with large phases, and/or large raw error rates, the
MTTF
calculated using
AVF+SOFR
shows significant-discrepancies from that using first principles. We also show that SoftArch, a previously proposed alternative method that does not make the
AVF+SOFR
assumptions, does not exhibit the above discrepancies.