As the technology of flash memory solid-state drives (SSDs)continues to advance, they are increasingly adopted in a wide spectrum of storage systems to deliver higher throughput atmore affordable prices. For example, it has been shown that
flash memory SSDs can outperform disk drives in terms ofthroughput, energy consumption, and cost-effectiveness fordatabase workloads [26,27]. Nevertheless, it is still true that the price per unit capacity of flash memory SSDs is higher than that of disk drives, and the market trend is likely to continue for the foreseeable future. Therefore, for applications dealing with large-scale data, it may be economically more
sensible to use flashmemory SSDs to supplement disk drives rather than to replace them.