The mechanical movement inherent in the operation of the hard disk poses access speed limits for many workloads and storage systems are consuming increasing amounts of power. Flash memory overcomes some key limitations of the hard disk including faster access to non-sequential data and significantly lower power usage. Encouraged by these advantages offered by flash memory and the recent emergence of high-capacity flash drives, this research will design and evaluate a hybrid system. Named HybridStore, this system will exploit complementary properties of these two media to provide improved performance, service differentiation, and thermal/power behavior in enterprise-scale storage.
HybridStore will comprise a dynamic data management solution that will adapt the use of available flash to workload conditions. Techniques for improving performance (e.g., moving non-sequential content to flash, use of flash as a write buffer) will be investigated. The investigators will explore how flash can facilitate improved service differentiation by reducing the variance of access times inherent in the operation of disks. Finally, the the feasibility of selected replication of popular content on disk and flash and diverting more IO traffic to flash during periods of thermal emergencies will be investigated. Power savings resulting from opportunities to slow down disks, without compromising performance, will also be explored. The investigators will implement a Linux-based prototype Direct-Attached Storage HybridStore system that will manage a hard disk drive and a SATA-enabled flash drive attached to the shared IO bus. To explore other hybrid configurations (such as flash on disk or RAID controller), a comprehensive simulator called HybridSim will be implemented. The PIs will enhance the graduate and undergraduate curricula at Penn State with topics related to this research.
