Application-aware solid-state drives (SSDs) with adaptive coding

Abstract

Application-aware solid-state drives (SSDs) with 2 adaptive coding schemes to improve reliability are presented. In NAND flash memory, a direct reliability trade-off exists between write/erase (W/E) cycle and data-retention (DR) time. Thus, SSDs can be used for applications that have long DR time and low W/E cycles, or short DR time with high W/E cycles. The n-out-of-8 level cell (nLC) scheme is proposed for low-cost, long-term, archive storage which is indispensable to preserve human digital data. nLC eliminates the memory states of the Triple-Level Cell (TLC) NAND flash memory from 8 to 7...4 levels. Universal asymmetric coding (UAC) is also proposed for cloud/security camera/enterprise storage environments which require high endurance but shorter DR time. Both nLC and UAC optimize coding based on the applications' required W/E cycle and DR. Bit-error rates (BERs) are improved by 79% and 52% with nLC and UAC, respectively.