A Thermal-Aware Physical Space Allocation Strategy for 3D Flash Memory Storage Systems

Three-dimensional (3D) flash memory stacks layers of data storage cells vertically to overcome the scaling limits in conventional planar NAND flash memory. Current 3D flash memory faces new challenges including thermal issues and complex manufacturing process. This paper presents TheraPhy, a novel thermal-aware physical space allocation strategy for three-dimensional flash memory storage systems. TheraPhy permutes the allocation of physical blocks. Consecutively accessed logical blocks are distributed to different physical locations in order to prevent the accumulation of hotspots. TheraPhy requires no changes to the file system, on-chip memory hierarchy, or hardware implementation of 3D flash memory. Based on TheraPhy, we present an address mapping strategy that is capable of determining the allocation of physical blocks based on their thermal status. We demonstrate the viability of the proposed technique using a set of extensive experiments. Experimental results show that TheraPhy can reduce the peak temperature by 15.39% with less than 1% extra erase overhead in comparison with the baseline scheme.