Hybrot: Towards Improved Performance in Hybrid SLC-MLC Devices

Abstract

There are two types of NAND flash memory - MLC (Multi -- Level Cell) and SLC (Single -- Level Cell). Low endurance and slower write performance in MLC NAND flash memory is a limitation to its usage in large scale solid state drives. On the other hand SLC NAND flash memory which has higher endurance and faster write performance is much more expensive than MLC devices. Hybrid SLC-MLC devices bridge the gap between the two by providing improved reliability at a low cost. In this paper, we propose an efficient architecture called Hybrot that aims at providing improved performance in hybrid SLC -- MLC devices and at the same time ensures maximum lifetime for the flash blocks. We propose a gray box approach for managing the SLC and MLC blocks which achieves the target write performance irrespective of the underlying flash management algorithms.