University of Miami School of Business Administration
Flash memories have high storage density and are used in memory cards, USB flash drives, and solid-state drives. The authors focus on Multi-Level Cell (MLC) Flash memories which store 2 or more bits per cell by supporting 4 or more voltage states. These have even greater storage density and are the dominant Flash memory technology. Unfortunately, NAND Flash memories suffer from write/read disturbs, data retention errors, bad block accumulation. Also, reliability of MLC memory is lower due to reduced gap between adjacent threshold levels. To enhance the reliability and support longer life-times, combinations of hardware and software techniques are used. These include wear leveling, bad block management and garbage collection.