Log-Structured Global Array for Efficient Multi-Version Snapshots

In exascale systems, increasing error rate -- particularly silent data corruption -- is a major concern. The Global ViewResilience (GVR) system builds a new model of application resilience on versioned global arrays. These arrays can be exploited for flexible, application-specific error checking and recovery. We explore a fundamental challenge to the GVR model -- the cost of versioning. We propose a novel log-structured implementation that appends new data to an update log, simultaneously tracking modified regions and versioning incrementally. We compare performance of log-structured arrays to traditional flat arrays using micro-benchmarks and three full applications, and show that versioning can be more than 10x faster, and reduce memory cost significantly. Further, in future systems with NVRAM, a log-structured approach is more tolerant onramp limitations such as write bandwidth and wear-out.