Current-aware scheduling for flash storage devices

As NAND flash memory has become a major choice of storage media in diversified computing environments, the performance issue of flash memory has been extensively addressed in many excellent designs. Among them, an effective strategy is to adopt multiple channels and flash-memory chips to improve the performance on data accesses. However, the degree of data access parallelism cannot be increased by simply increasing the number of channels and chips in the storage device, because it is seriously limited by the maximum current constraint of the bus interface and affected by the access patterns of user data. As a consequence, to maximize the degree of access parallelism, it is of paramount significance to have a proper scheduling strategy to determine the order that read/write requests are served. In this paper, a current-aware scheduling strategy for read/write requests is proposed to maximize the read performance without violating the bus current constraint and without missing (the deadline of) written data. The proposed strategy is then evaluated through a series of experiments, in which the results are quite encouraging.