标题: 以记忆体为基底的嵌入式储存系统之设计与研究
A Study on the Design of Memory Based Embedded Storage Systems
作者: 姜美玲
Mei-Ling Chiang
张瑞川
Prof. Ruei-Chuan Chang
资讯科学与工程研究所
关键字: 快闪记忆体;清除策略;储存系统;资料丛集;flash memory;Cleaning policies;Storage systems;Data clustering
公开日期: 1998
摘要: 由于轻、薄、短、小及省电的要求,许多消费性民生电子产品或嵌入式设备都使用具有电池供电的记忆体或快闪记忆体来储存资料。传统的储存系统都是考量硬碟的特性来做最佳化的设计,然而记忆体及快闪记忆体的特性与硬碟截然不同,因此储存系统有重新设计的必要。例如,以快闪记忆体为基底的储存系统必需克服来自硬体的限制:快闪记忆体写入时间比读取时间慢、储存区要先被抹除后才能再被写入,以及有写入次数的限制。而以记忆体为基底的储存系统要能保护所储存的资料,以避免资料的毁坏或不一致。
在本论文□,针对记忆体的特性我们设计了一个以记忆体为基底的物件储存系统,此系统使用了改良的夥伴系统 (buddy system) 来减少内部零碎 (internal fragmentation),并且利用资料压缩技术来减少对储存空间的需求,以及提供交易处理 (transaction processing) 来保持资料的一致性。实验显示此系统不仅能有效地管理有限的储存空间,并且能很有效率地存取物件。
此外,针对快闪记忆体的特性,我们提出一个新的储存空间管理方式,并且分析与设计了许多清除策略,目的是要对储存区做均衡的抹除,以及减少抹除的动作。透过实作与模拟实验证明,此储存空间管理方式配合有效率的清除策略,不仅能大幅地提升系统的效能,亦能延长快闪记忆体的使用寿命,以及减少耗电量。
Due the requirements of small size, light weight, and low power consumption, several consumer electronics or embedded devices use battery-backed RAM or flash memory to replace hard disk drives for data storage. However, conventional storage system designs are all optimized toward hard disks while RAM and flash memory are totally different from hard disks. These hardware characteristics impose the need of redesigning storage systems for them. For example, storage systems should overcome the limitations of flash memory such as write access times higher than read access times, the need to erase flash memory before rewriting it, and a limited number of erase cycles in the lifetime of the device. Data stored in battery-backed RAM must be carefully guarded against power and crashes to refrain from losing information or data corruption.
In this thesis, we have designed and implemented a RAM-based object storage system that takes advantage of memory characteristics and uses RAM-based storage efficiently. An enhanced buddy system is employed to reduce internal fragmentation. Data compression is used to reduce storage space requirements and transaction processing is provided for data consistency and fault recovery. Performance evaluations show that this storage system is efficient in object access and in utilizing limited storage space.
For flash memory research, we have proposed the partitioned log-based flash memory management method. Various cleaning policies are analyzed and newly proposed, in order to reduce the number of erase operations performed on flash memory and to evenly wear the flash memory. Empirical evaluations through practical implementation and trace-driven simulations show that system throughput is largely improved, flash memory lifetime is substantially prolonged, and power consumption is greatly reduced.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT870394002
http://hdl.handle.net/11536/64139
显示于类别:Thesis