Architecture and Technologies of Flash Memory Based Solid State Drives

Flash memory based solid state drives (SSDs) are widely deployed in personal computers, data centers, and cloud storages given their well identified advantages, such as high performance, low power consumption and non-volatile property. In recent years, with the development of process technology and micro electronic technology, the features of SSDs are greatly changed. First, detailed storage mechanism of flash cell is introduced, including architecture of flash cell and flash block, programming method, and basic operation of SSDs. Then, several SSD controller key technologies are presented, including buffer device, flash translation layer, garbage collection, data allocation, wear leveling and error correction code. These technologies are used to well support normal operation of SSDs. Additionally, the parallel architecture of SSDs which is used to boost the performance of SSDs, is discussed and related constraints are also presented while several previous works on parallelism exploration are analyzed. Next, since the scaling of SSD has evolved from planar (2D) to 3D stacking, 3D SSD is introduced as a new type of SSDs that can provide larger capacity compared with traditional planar SSD. In this paper, the characteristics of 3D SSDs’ vertical architecture, performance and lifetime are analyzed. Also, the disadvantages of previous works on 3D SSD performance and lifetime optimizations are discussed. Finally, current state of SSDs is summarized and possible future research works are given.