Assessing the Impact of Partial Verifications against Silent Data Corruptions

Abstract

Silent errors, or silent data corruptions, constitute a major threat on very large scale platforms. When a silent error strikes, it is not detected immediately but only after some delay, which prevents the use of pure periodic checkpointing approaches devised for fail-stop errors. Instead, checkpointing must be coupled with some verification mechanism to guarantee that corrupted data will never be written into the checkpoint file. Such a guaranteed verification mechanism typically incurs a high cost. In this paper, we assess the impact of using partial verification mechanisms in addition to a guaranteed verification. The main objective is to investigate to which extent it is worthwhile to use some light cost but less accurate verifications in the middle of a periodic computing pattern, which ends with a guaranteed verification right before each checkpoint. Introducing partial verifications dramatically complicates the analysis, but we are able to analytically determine the optimal computing pattern (up to the first-order approximation), including the optimal length of the pattern, the optimal number of partial verifications, as well as their optimal positions inside the pattern. Performance evaluations based on a wide range of parameters confirm the benefit of using partial verifications under certain scenarios, when compared to the baseline algorithm that uses only guaranteed verifications.

Which Verification for Soft Error Detection?

“…These formulas provide first-order approximations to the length of the optimal pattern in the corresponding scenario, and are valid only if the resilience parameters satisfy C, V * µ. To the best of our knowledge, the only analysis that includes partial verifications is the recent work [11], which deals with patterns that may include one or several detector(s), but all of the same type. While most applications accept several detector types, there has been no attempt to determine which and how many of these detectors should be used.…”

“…All of these results assume the use of guaranteed verifications only. As already mentioned, the only analysis that includes partial verifications in the pattern is the recent work of [11].…”

“…However, [11] restricts to a single type of partial verification. In this paper, we provide the first theoretical analysis that includes partial verifications of different types.…”

“…When all the partial verifications in the pattern have the same type, i.e., g k = g for all 1 ≤ k < n, we retrieve the result of [11], obtaining f * re = 1 2 1 +…”

Emergent Computation

“…In this section we explain how to derive the optimal pattern of interleaving checkpoints and verifications. An extended presentation of the results is available in [2,4,10].…”