A Write-Related and Read-Related DRAM Allocation Strategy Inside Solid-State Drives (SSDs)

Abstract

Although NAND flash memory has the advantages of small size, low-power consumption, shock resistance, and fast access speed, NAND flash memory still faces the problems of “out-of-place updates,” “garbage collection,” and “unbalanced execution time” due to its hardware limitations. Usually, a flash translation layer (FTL) can maintain the mapping cache (in limited DRAM space) to store the frequently accessed address mapping for “out-of-place updates” and maintain the read/write buffer (in limited DRAM space) to store the frequently accessed data for “garbage collection” and “unbalanced execution time”. In this article, we will propose a write-related and read-related DRAM allocation strategy inside solid-state drives (SSDs). The design idea behind the write-related DRAM allocation method is to calculate the suitable DRAM allocation for the write buffer and the write mapping cache by building a statistical model with a minimum expected value of writes for NAND flash memory. To further reduce reads in NAND flash memory, the design idea behind the read-related DRAM allocation method is to adopt a cost-benefit policy to reallocate the proper DRAM space from the write buffer and the write mapping cache to the read buffer and the read mapping cache, respectively. According to the experimental results, we can demonstrate that the proposed write-related and read-related DRAM allocation strategy can reduce more reads/writes in NAND flash memory than other methods to improve the response time.