This papers reviews the increasing role of NAND flash memory in storage architectures. NAND flash has enjoyed a phenomenal growth rate in storage capacities as well as a steady decline in pricing during the past few years. These developments have enabled NAND to enter and possibly change or displace some traditional storage architectures. However, besides cost, NAND flash memory has some reliability and performance issues that will slow its adoption into all storage architectures. This paper will analyze the advantages and disadvantages of this technology and the implications to the current and possible future storage architectures. Moreover, we will analyze NAND flash future density and costs trends and compare them with the traditional hard disk drive.

Four alternative implementations for achieving higher data rates in a disk subsystem (parallel heads without replication, parallel heads with replication, parallel actuators without replication, and parallel actuators with replication) are studied. Focus is on the tradeoffs between the number of devices and the number of data paths while keeping the number of physical devices constant (which may keep the cost roughly constant). The performance advantages and limitations of the alternative implementations are analyzed using an analytic queuing model and compared to a conventional disk subsystem. The study shows that parallel heads with replication from a single actuator performs the best for the average application environments, although other configurations may be more cost-effective.>