An SSD-based disk cache architecture and its application to data system of data center of Meridian Project

Solid-State Drivers (SSD) are integrated in server storage hierarchy as a second tier of disk cache between DRAM and disks for caching more data from disks to meet the increasingly intensive I/O demands. Unfortunately, available state-of-art hybrid storage architectures cannot fully exploit SSDs' potentials and shorten their lifetime. In this paper, RAF (Random Access First), a hybrid storage architecture that combines an SSD based disk cache and a disk drive subsystem, is proposed. RAF focuses on improving the system performance while extending the lifetime of SSD through providing priority to caching random-access data. Random-access and sequential-access data are identified by sequence detection scheme, and they will be served by SSD and Hard Disk Drive (HDD) respectively. RAF is implemented in Linux kernel 2.6.30.10. The results of experiments to apply it to the simulation and real data systems of Data Center of Meridian Project show that RAF can improve the performance by an average rate of 17% and reduce the flash wear by 53% compared with the state-of-art Flash Cache architecture.