Bridging the I/O performance gap for big data workloads: A new NVDIMM-based approach

The long I/O latency posts significant challenges for many data-intensive applications, such as the emerging big data workloads. Recently, the NVDIMM (Non-Volatile Dual In-line Memory Module) technologies provide a promising solution to this problem. By employing non-volatile NAND flash memory as storage media and connecting them via DIMM (Dual Inline Memory Module) slots, the NVDIMM devices are exposed to memory bus so the access latencies due to going through I/O controllers can be significantly mitigated. However, placing NVDIMM on the memory bus introduces new challenges. For instance, by mixing I/O and memory traffic, NVDIMM can cause severe performance degradation on memory-intensive applications. Besides, there exists a speed mismatch between fast memory access and slow flash read/write operations. Moreover, garbage collection (GC) in NAND flash may cause up to several millisecond latency. This paper presents novel, enabling mechanisms that allow NVDIMM to more effectively bridge the I/O performance gap for big data workloads. To address the workload heterogeneity challenge, we develop a scheduling scheme in memory controller to minimize the interference between the native and the I/O-derived memory traffic by exploiting both data access criticality and resource utilization. For NVDIMM controller, several mechanisms are designed to better orchestrate traffic between the memory controller and NAND flash to alleviate the speed discrepancy issue. To mitigate the lengthy GC period, we propose a proactive GC scheme for the NVDIMM controller and flash controller to intelligently synchronize and transfer data involving in forthcoming GC operations. We present detailed evaluation and analysis to quantify how well our techniques fit with the NVDIMM design. Our experimental results show that overall the proposed techniques yield 10%~35% performance improvements over the state-of-the-art baseline schemes.