ECC-Aided RAID for Reliability Improvement of SSD

In the field of solid state drive (SSD), redundant array of inexpensive disk (RAID) is of great use due to its reliability and performance. In terms of reliability, RAID can be further enhanced with the help of error-correction code (ECC), which is another core technology for SSD applications. Recently, joint ECC-RAID schemes have been proposed for the reliability of SSD. Especially, due to high reliability with low computational complexity, joint ECC-RAID schemes based on RAID-5, denoted as ECC-RAID-5, are popularly adopted to devices as well as systems of data storage. In this paper, a new family of joint ECC-RAID schemes, called ECC-aided RAID (EA-RAID), are proposed to further improve the reliability of the joint ECC-RAID schemes in the data storage applications. In the EA-RAID, new types of data checking and regenerating algorithms based on soft-decision (SD) are introduced to enhance the error-correcting capability of the cooperative ECC decoding. The EA-RAID increases error-correction capability as at least 15% and 7% gain compared with the ECC-only schemes and the conventional ECC-RAID-5, respectively. The improvement is demonstrated by productized SSD based on virtuaI3-bit-over multi-level cell (MLC) NAND. It is expected that the proposed technologies can be introduced as a potential solution for next generation NAND.