NVRAM-aware Logging in Transaction Systems

Emerging byte-addressable, non-volatile memory technologies (NVRAM) like phase-change memory can increase the capacity of future memory systems by orders of magnitude. Compared to systems that rely on disk storage, NVRAMbased systems promise significant improvements in performance for key applications like online transaction processing (OLTP). Unfortunately, NVRAM systems suffer from two drawbacks: their asymmetric read-write performance and the notable higher cost of the new memory technologies compared to disk. This paper investigates the cost-effective use of NVRAM in transaction systems. It shows that using NVRAM only for the logging subsystem (NV-Logging) provides much higher transactions per dollar than simply replacing all disk storage with NVRAM. Specifically, for NV-Logging, we show that the software overheads associated with centralized log buffers cause performance bottlenecks and limit scaling. The per-transaction logging methods described in the paper help avoid these overheads, enabling concurrent logging for multiple transactions. Experimental results with a faithful emulation of future NVRAM-based servers using the TPCC, TATP, and TPCB benchmarks show that NV-Logging improves throughput by 1.42 2.72x over the costlier option of replacing all disk storage with NVRAM. Results also show that NV-Logging performs 1.21 6.71x better than when logs are placed into the PMFS NVRAM-optimized file system. Compared to state-of-theart distributed logging, NV-Logging delivers 20.4% throughput improvements.