Co-Active: A Workload-Aware Collaborative Cache Management Scheme for NVMe SSDs

Abstract

When it comes to NAND Flash-based solid-state disks (SSDs), cache can narrow the performance gap between user-level I/Os and flash memory. Cache management schemes impose relentless impacts on the endurance and performance of flash memory. A vast majority of existing cache management techniques adopt a passive data-update style (e.g., GCaR, LCR), thereby undermining response times in burst I/O requests-based applications <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> 1.Burst I/O requests must be served in a real-time manner. This type of I/O access pattern is prevalent in data-intensive workloads.. To address this issue, we propose a collaborative active write-back cache management scheme, called Co-Active, customized for I/O access patterns and the usage status of a flash chip. We design a hot/cold separation module to determine whether data is cold or hot in workload. When a flash chip is idle, cold and dirty data in the cache is flushed into the idle flash chip to produce clean data. To curtail cache replacement cost, clean data are preferentially evicted amid the procedure of cache replacement. A maximum write-back threshold is configured according to the level of burst I/O requests in workload. This threshold is intended to avert redundant write I/Os flushing into flash memory, thereby boosting the endurance of flash memory. The experiments are conducted to validate the advantages of Co-Active in terms of average response time, write amplification, and erase count. The findings unveil that compared with the six popular cache management schemes (LRU, CFLRU, GCaR_CFLRU, LCR, and MQSim), Co-Active (1) slashes the average response time by up to 83.89 percent with an average of 32.7 percent; (2) drives up the performance cliff degree by up to 76.4 percent with an average of 42.3 percent; and (3) improves write amplification rate by up to 60.5 percent with an average of 5.4 percent.