MU-RMW: Minimizing Unnecessary RMW Operations in the Embedded Flash with SMR Disk
Chenlin Ma1,a, Zhuokai Zhou1,b, Yingping Wang1,c, Yi Wang1,d and Rui Mao1,2
1College of Computer Science and Software Engineering, Shenzhen University, Shenzhen, China
achenlin.ma@szu.edu.cn
b2110276021@email.szu.edu.cn
c2100271073@email.szu.edu.cn
dyiwang@szu.edu.cn
2Shenzhen Institute of Computing Sciences, Shenzhen, China
mao@szu.edu.cn
ABSTRACT
Emerging Shingled Magnetic Recording (SMR) Disk can improve the storage capacity significantly by overlapping multiple tracks with the shingled direction. However, the shingledlike structure leads to severe write amplification caused by RMW operations inner SMR disks. As the mainstream solid-state storage technology, NAND flash has the advantages of tiny size, costeffective, high performance, making it suitable and promising to be incorporated into SMR disks to boost the system performance. In this hybrid embedded storage system (i.e., the Embedded Flash with SMR disk (EF-SMR) system), we observe that physical flash blocks can contain a mixture of data associated with different SMR data bands; when garbage collecting such flash blocks, multiple RMW operations are triggered to rewrite the involved SMR bands and the performance is further exacerbated. Therefore, in this paper, we for the first time present MU-RMW to guarantee data from different SMR bands will not be mixed up within the flash blocks with an aim at minimizing unnecessary RMW operations. The effectiveness of MU-RMW was evaluated with realistic and intensive I/O workloads and the results are encouraging.
Keywords: Shingled Magnetic Recording, NAND Flash, Address Mapping, Cache Management.
