Enhanced Flash Swap: Using Nand Flash As A Swap Device With Lifetime Control

Modern mobile consumer electronics require more memory than ever, as more complicated and memory-heavy features are becoming more common. One of the ways to improve memory space is to have NAND flash as a swap device. However, naively adopting such approach has reliability issues, due to the limited lifetime of NAND flash devices. In this paper, we propose a new solution, Enhanced Flash Swap (EFS). EFS uses NAND flash as a swap device with a careful control of its lifetime. This paper introduces several techniques to address the issue of lifetime on flash-based swap, including deduplication, compression, buffering and physical block management. We also present how to optimize write I/O patterns for a longer lifetime through an intensive experiment of WAF estimation on real devices. Experimental results show that EFS has greater lifetime by 3.6x - 138x than traditional swap system.