SSD相关技术的的研究.ppt

SSD相关技术研究 武汉大学计算机学院系统结构研究所 何水兵 许先斌 杨元华 2010.11.25 主要内容 SSD简介 Flash-based SSD特点 SSD内部结构 SSD关键技术 SSD设计方案 SSD相关项目 SSD工业界厂商 实验平台 参考资料 1 SSD(Solid State Disk)简介 基于半导体的存储设备 1.1 SSD分类 1.2 SSD应用领域 个人计算机BIOS 存储 嵌入式系统的标准存储器 在某些笔记本电脑中代替磁盘作为外存储器 企业级存储的高端存储阵列 1.3 数据访问时间 1.4 随机I/O性能 1.5 能耗 1.6 性能和价格 2 Flash-based SSD 特点 2.1 SSD优点 Reliability in portable environments and no noise No moving parts Faster start up Does not need spin up Extremely low read latency No seek time (25 us per page/4KB) Deterministic read performance The performance does not depends on the location of data 2.2 SSD缺点 Cost significantly more per unit capacity 3$/GB vs. 0.15$/GB Limited write erase time 100000 writes for SLC (MLC is even fewer) high endurance cells may have an 1-5 million But some files still need more Weaver leaving to spread writes all over the disk Slower write speeds because of the erase blocks are becoming larger and larger(1.5 ms per erase) For low capacity flash SSDs, low power consumption and heat production when in active use. High capacity SSDs may have significant higher power requirements 2.4 Flash重写问题 3 SSD内部结构 3.1 Flash 内存 Flash memory A non-volatile semiconductor memory device Key feature : To overwrite data, the memory cell should be erased first. Kinds of flash memory NOR Introduced by Intel in 1988 Randomly access data, like a computer’s main memory Use for executing program code NAND Introduced by Toshiba in 1989 Smaller and denser. → NAND is better at storing data. Faster erase and write time NAND vs. NOR NAND Flash Organization of NAND flash memory Small-block flash memory Each page is (512 + 16) bytes long 32 pages in each block Large-block flash memory Each page is (2048 + 64) bytes long 64 pages in each block NAND Flash Primitive operations of NAND flash memory Read page (chip #, block #, page #) ~20 us Write (program) page (chip #, block #, page #) ~200 us Erase block (chip #, block #) ~2 ms 3.2 NAND FLASH连接 Package: 共享一个bus通道的一组flash dies。 Die: 由一组planes