Retention Time Based Data Management Policy for Improving the Lifespan of SSDs

As the density of the flash memory continues to increase, the endurance issue of the flash memory based SSD is becoming more important. Reducing the retention time is one of the solutions to improve the lifespan of SSD. This is because the data stored on the SSD with short retention time requires less energy power when the data is erased by garbage collection; the less energy power can prolong the lifespan of SSD. For this reason, some researchers focus on the retention time to enhance the lifespan of SSD. However, previous work considers only the temporal locality, and therefore it reveals limited enhancement on the lifespan of SSD. In this paper, we propose a novel data classification scheme that considers the retention time of each flash block for efficient retention management and ultimately extends the lifespan of SSD. Our experiments show that the proposed scheme improves the lifespan of SSD by up to 7.2 times over the conventional SSD, with negligible performance degradation.