S-RAC: SSD Friendly Caching for Data Center Workloads

Current data-center applications tend to process increasingly large volume of data sets. The caching effect of page cache is reduced by its limited capacity. Emerging flash-based solid state drives (SSD) have latency and price advantages compared to hard disk and DRAM. Thus, SSD-based caching is widely deployed in data centers. However, SSD caching faces two challenges. First, SSD has limited write endurance, which requires cache manager to reduce write amount to SSD. Second, data-center workloads exhibit a diverse I/O access patterns, which requires one to figure out SSD caching friendly access patterns. This paper first classifies 6 I/O access patterns among 32 data-center workloads using a cost-benefit analysis. We derive implications for designing SSD cache from analyzing the access patterns. We then propose an SSD cache manager S-RAC with re-adding blocks and ghost cache adaptation to retain SSD friendly blocks in SSD. The experimental evaluation shows the efficiency of S-RAC in reducing SSD write amount while improving/maintaining cache hit ratio.