Exploiting Data Longevity for Enhancing the Lifetime of Flash-based Storage Class Memory

This paper proposes to exploit the capability of retention time relaxation in flash memories for improving the lifetime of an SLC-based SSD. The main idea is that as a majority of I/O data in a typical workload do not need a retention time larger than a few days, we can have multiple partial program states in a cell and use every two states to store one-bit data at each time. Thus, we can store multiple bits in a cell (one bit at each time) without erasing it after each write -- that would directly translates into lifetime enhancement. The proposed scheme is called Dense-SLC (D-SLC) flash design which improves SSD lifetime by 5.1X--8.6X.