TailCut: improving performance and lifetime of SSDs using pattern-aware state encoding

Although lateral charge spreading is considered as a dominant error source in 3D NAND flash memory, little is known about its detailed characteristics at the storage system level. From a device characterization study, we observed that lateral charge spreading strongly depends on vertically adjacent state patterns and a few specific patterns are responsible for a large portion of bit errors from lateral charge spreading. We propose a new state encoding scheme, called TailCut, which removes vulnerable state patterns by modifying encoded states. By removing vulnerable patterns, TailCut can improve the SSD lifetime and read latency by 80% and 25%, respectively.