The Design And Implement Of Solid State Disk Cache System

With the rapid development of cloud computing and big data,the storage system,which is the cornerstone,needs to provide high storage capacity and high performance at low cost.While at present any one of the storage devices,such as solid state disk and hard disk drive,can not meet the above requirements alone.Hybrid storage system takes full advantage of the characteristics of different storage device to support large-capacity,but also ensures high performance without too much extra cost.Therefore,hybrid storage system is becoming current research focus and research direction.This paper conducted in-depth research on the key technologies in hybrid storage system.Then the SSD cache system based on SSD and HDD,qscache was designed and implemented.The main work of this paper is as follows:1.The performance,cost and capacity of current wide-used storage devices were analyzed and compared.2.Several key technologies including system architecture,data mapping strategy,hot data identification strategy,data write back/migration strategy,optimal combination of storage devices in hybrid storage systems were studied deeply.3.Three widely-used open source hybrid storage systems were studied,and their performance and characteristics were analyzed and compared.4.The design and implementation of hybrid storage system qscache including the support of flexible mapping from SSD to HDD.5.The source code of Device Mapper framework in Linux kernel was modified to support a new interface,based on which,the qscache system supports assigning IOPS for different processes based on weight.6.The performance of the qscache system was tested,and the results were analyzed.The test results shows that the performance of qscache system was close to flashcache,and mapping between several SSDs and HDDs was implemented.The modification of Linux kernel supports the request-based mode qscache system,based on which assigning IOPS for different processes based on weight was supported.This research provides a reference for the design and implementation of other hybrid storage systems.