Research On File Cache Management Strategy Based On Dynamic Hybrid SSD

With the continuous development of NAND flash,and thanks to its high performance and large capacity,Solid State Drives(SSDs)based on NAND flash have become the mainstream storage medium.With the development of manufacturing processes and the need to cut costs,high-density and low-cost flash media,which can store multiple bits of information in a single flash storage cell,have dominated the mainstream market.How-ever,this kind of high density flash particle has some problems,such as poor I/O perfor-mance and limited write endurance.To reconcile capacity and performance,hybrid SSDs were invented,which has both high-speed flash media(such as Single Level Cell,SLC)to meet performance requirements and high-density media(such as Quad Level Cell,QLC)to meet capacity requirements.Due to the high-capacity nature of dynamic hybrid SSDs,end-to-end devices equipped with such storage can easily obtain large amounts of space for caching network data to improve network access performance.However,due to the dynamic conversion charac-teristics of the internal storage medium unit,the I/O performance of dynamic hybrid SSDs tends to decline with the increase of capacity.Therefore,how to effectively manage file cache based on dynamic hybrid SSDs has not been carefully studied.This article addresses a scenario where part of the space of a dynamic hybrid SSD is used as a file cache on an end-to-end device.In this paper,a real dynamic hybrid SSD device is studied,and based on the test results,a file cache management for dynamic hybrid SSD is designed.The main contributions of this paper are as follows:1.Lots of testing and analysis for dynamic hybrid SSDs are performed.This paper selected the typical dynamic hybrid SSD products in the market,did a lot of I/O testing and analysis,and obtained a general characteristic curve.2.A file cache space management strategy based on characteristic curve is designed.The average I/O performance of a storage device is improved by dynamically ad-justing the maximum available cache space in different storage phases3.A cache file sifting strategy based on characteristic curve is designed.The dynam-ically adjusted type elimination scheme and the increasingly strict cache file access policy limit the opportunities for low-value files to enter the flash cache and reduce the I/O write volume and I/O competitionThis paper designs and implements a dynamic cache file management strategy for dy-namic hybrid SSD,and named DFCache(Dynamic File Cache).Two components,cache space management module and cache file sifting module are introduced in detail.In ad-dition,experiments were carried out on a real dynamic hybrid SSD device to verify the effectiveness of the proposed scheme.Experiments show that DFCache can effectively improve the local I/O performance when the local device is used as the cache by control-ling the size of the cache space and filtering the cache file.Compared with other schemes,DFCache improves I/O performance when using dynamic hybrid SSD as cache,and it achieves 3.7 times improvement in some performance indicators.