Co-Active: A Workload-Aware Collaborative Cache Management Scheme for NVMe SSDs
Co-Active: A Workload-Aware Collaborative Cache Management Scheme for NVMe SSDs
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DOI：
10.1109/tpds.2021.3052028
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发表时间：
2021-06
影响因子：
5.3
通讯作者：
Hui Sun;Shangshang Dai;Jianzhong Huang;X. Qin
中科院分区：
文献类型：
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作者：
Hui Sun;Shangshang Dai;Jianzhong Huang;X. Qin
对于基于NAND闪存的固态硬盘(SSD)，缓存可以缩小用户级I/O与闪存之间的性能差距。高速缓存管理方案对闪存的耐用性和性能施加了无情的影响。绝大多数现有高速缓存管理技术采用被动数据更新风格(例如gCar、LCR)，从而降低了基于突发I/O请求的应用程序的响应时间11.突发I/O请求必须以实时方式提供服务。这种类型的I/O访问模式在数据密集型工作负载中很常见。。为了解决这一问题，我们提出了一种协作式主动回写缓存管理方案，称为CoActive，根据闪存芯片的I/O访问模式和使用状态进行定制。我们设计了一个冷热分离模块来判断工作负载中的数据是冷的还是热的。当闪存芯片空闲时，缓存中的冷脏数据被刷新到空闲的闪存芯片中，以产生干净的数据。为了降低缓存替换成本，在缓存替换过程中优先清除干净数据。根据工作负载中突发I/O请求的级别配置最大回写阈值。此阈值旨在避免冗余写入I/O刷新到闪存，从而提高闪存的耐用性。通过实验验证了CoActive在平均响应时间、写入放大和擦除计数方面的优势。研究结果表明，与六种流行的缓存管理方案(LRU、CFLRU、gCar_CFLRU、LCR和MQSim)相比，Co-Active(1)将平均响应时间降低了83.89%，平均为32.7%；(2)将性能悬崖程度提高了76.4%，平均为42.3%；(3)将写入放大率提高了60.5%，平均为5.4%。
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 applications11.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.