Schemes for Extending the Lifetime of SSD

Abstract

The limited use lifetime is a significant drawback of the solid state disk (SSD). When the P/E cycles exceed the nominal endurance limit, the entire SSD is rendered non-functional as worn out. As the low endurance, the MLC Flash based SSD is not suitable used in lifetime-aware applications and the total-byte-written of conventional MLC SSD is much less than SLC SSD. In this paper, we proposed an Adaptively Level Adjusting Scheme to use the MLC Flash dynamically to storage different amount of data levels through the entire lifetime. The result shows that the MLC SSD adopting this method could be totally written 4.8X more data than conventional MLC SSD and 16.5% more than SLC SSD. Another simple method named Post Life Slavaging Scheme is also proposed to benefit from the post life of a MLC SSD. It can extend the real P/E endurance by 2X when the user capacity reduced to 92% of original cacapcity.