一种基于裸闪存的Key-Value数据库优化方法

A Key-Value Database Optimization Method Based on Raw Flash Device

近年来,非关系型的key-value数据库得到越来越广泛的应用.然而,目前主流的key-value数据库或者是基于磁盘设计的,或者是传统的基于文件系统和闪存转换层FTL来构建的,难以发挥闪存存储设备的特性,限制了I/O的并发性能,且垃圾回收过程复杂.设计并实现了一种基于裸闪存的keyvalue数据管理架构Flashkv,通过用户态下的管理单元进行空间管理和垃圾回收,充分利用了闪存设备内部的并发特性,并简化了垃圾回收过程,去除了传统文件系统和FTL中的冗余功能,缩短了I/O路径.提出了基于闪存特点的I/O调度技术,优化了闪存的读写延迟,提高了吞吐率;提出了用户态缓存管理技术,降低了数据写入量和频繁系统调用所带来的开销.测试结果表明,Flashkv性能是levelDB的1.9~2.2倍,写入量减少60%~65%.

In recent years,NoSQL key-value data bases have been widely used.However,the currentmainstream key-value data basesare based either on disk,orontraditional file system and flashtranslationlayer,which makesit difficult to utilize the characteristics of flash devices,and alsolimits1/Oconcurrency of flash devices.Moreover,garbagecollection processunder such kind of architectureis complex.This paper designs and implements Flashkv,akey-value data management architecturebasedonraw flash device.Flashkv doesn,tusefilesystem and flashtranslation layer,instead,it,s spacemanagement and garbage collection are done by the management unitin the user mode.Flashkv makes fulluse of the concurrentfeatures inside the flash device,and simplifies the garbagecollection process and removesredundant functionmodules which existin both traditional filesystem and flash translation layer,and alsoshortens the I/Opath.This paper proposes I/O scheduling technology based on the characteristics of flash memory,which reducesread and writelatency of flash memory and improves through put.The user modecache management technology is proposed,which reduceswriteamount and alsothecost of frequent system calls.Testresults show tha tFlashkv'sperformance is1.9to2.2times that of levelDB and the write amountreduces by60%to65%.