Exploiting Write Heterogeneity of Morphable MLC/SLC SSDs in Datacenters with Service-Level Objectives
Abstract: Given the needs of data-intensive intensive web services and cloud computing applications, storage centers play an important role in serving the demanded data access while jointly considering low cost, qualified performance, and good scalability. To manage peak workloads loads with performance requirements for read/write latencies, overprovisioning more storage nodes is common but also increases total cost as well as power consumption. Recently, due to the growing capacity and dropping price, NAND-flash-based based Solid Solid-State Drives rives (SSDs) have become an attractive storage solution in datacenters. In this work, we exploit the write heterogeneity in Multi-Level-Cell Cell (MLC) NAND flash memory to meet Service Service-Level Level Objectives (SLOs) of applications and to avoid storage overprovision. In MLC NAND flash memory, a memory cell can be programmed as a Single Single-Level Level Cell (SLC) or a multimulti level cell at runtime, and SLC writes take shorter latency with the cost of larger consumed capacity. The proposed SLO SLO-aware aware morphable SSD design seeks to meet et the SLO requirement by deciding the write mode of each write request while minimizing the number of SLC writes. Experimental results show that the proposed design meets the SLO requirement for all of the tested I/O traces with less than 2.8 percent extraa erase counts in average, while conventional MLC SSDs require up to 2.375 times storage overprovision to meet the SLO requirement.