Research And Implementation Of Nonvolatile Caching Mechanism For SSD

As an important part of the computer system,the storage system has always been an important factor affecting the overall performance of the computer system.With the advent of the era of big data,big data on the storage area has brought new challenges.With the Flash SSD based NAND access to the external storage market,it is completely different from the new characteristics of the disk to create a new opportunity to optimize the storage structure.However,SSD itself is written and amplified,the random write performance is poor,the number of P/E is limited,as well as the interference to cause the random update and other issues will affect the performance and life of SSD.In this paper,we mainly study the SSD oriented non-volatile cache mechanism,the main work and innovation of this paper are as follows:First of all,this study is proposed by using SSD itself to cache the coming requests to SSD itself,which we called SSD caching SSD,SCS,and we have also reali-zed the system,thereby reducing the random latency,reading disturbs and SSD lifetime.Secondly,a kind of I/O sequential detection algorithm is proposed.Because SSD itself is more sensitive to the order of write requests.For the sequential write request performance would be better than the random write request,at the same time in order to reduce the amount of requests to the SCS' cache area,without compromising the performance of the system through the sequence I/O sensing algorithm to filter out chunks and consecutive requests,so as to improve the overall efficiency of the SCS system.We propose an asynchronous insertion strategy to reduce the occurrence of interference and reduce the unnecessary garbage collection.SCS mainly through the SSD cache SSD this new mechanism,to extend the life of the SSD,improve the performance of SSD random write.Then this paper designs a new garbage collection strategy for cache area.Because the cache area has a lot of dirty data.These dirty data need to migrate back to the data area in a certain period of time.However,directly to the buffer dirty data written back to the data area,it will produce a large number of random write.Therefore,through the proposed caching strategy,so that all requests in the cache system can be carried out in the form of order,so as to greatly improve the performance of the system.Finally,based on the device kernel mapper(DM)mechanism of Linux,we have a realization of a kernel module,so as to complete the design and implementation of the overall cache system.Through the DM mechanism to realize the data redirection.This kernel module does not need to make too many changes to the operating system,which has a high flexibility and a wide range of applicability.Experimental results show that,compared with the traditional single disk,the performance is improved by about 5 times compared to the traditional one.At the same time for the reality of the load,such as Webserver,Filesercer,Mailserver and Database,performance relative to the SSD increased by 63.54%,28.06%,95.14% and 69.98% respectively,and the response time reduced by 43.92%?28.17%?70.28%?56.12%.