NVRC:一种面向NVM的写限制日志方案

非易失性内存(Non-Volatile Memory,NVM)具有支持按字节寻址、持久性、存储密度高、读写延迟低等特点,因此成为解决DRAM(Dynamic Random Access Memory)容量有限问题的首选技术。随着数据库系统中NVM的引入,传统的日志技术需要考虑如何适应NVM特性。首先总结了已有的面向NVM的日志技术研究,进而提出了一种尽可能限制NVM写操作的数据库日志方案NVRC(Non-Volatile Record-updating with Cacheline)。文中提出了结合异地更新和原地更新的日志管理方案。具体而言,NVRC在异地更新的“影子记录”的基础上,引入了“缓存行原地更新”策略,并通过代价分析选择合理的日志更新策略,从而减少对NVM的写操作。采用DRAM模拟NVM的方式在YCSB测试负载上进行了实验,并对比了NVRC与传统的WAL(Write Ahead Log)以及NVM感知的PCMLx(PCMLoggingx)方法。结果表明,NVRC的NVM写次数在修改均匀的情况下比WAL和PCMLx分别减少了54%和17%,同时更新性能分别提升了59%和10%。

NVRC:Write-limited Logging for Non-volatile Memory

Non-volatile memory(NVM)has the characteristics of byte addressing,persistence,high storage density,low read-write delay,etc.,so it becomes the preferred technology to solve the problem of limited DRAM(Dynamic Random Access Memory)capacity.With the introduction of NVM in database systems,traditional log technologies need to consider how to adapt to the characteristics of NVM.This paper first summarizes the existing research on NVM oriented log technologies,and then proposes a database log scheme called NVRC(Non-Volatile Record-updating with Cacheline)that limits NVM write operations as much as possible.This paper puts forward a log management scheme which combines out-place and in-place update.Specifically,on the basis of out-place-update-based shadow records,NVRC introduces the strategy of“in-place cache line update”,and dynamically selects the log update strategy through cost analysis,so as to reduce the writes to NVM.This paper uses DRAM to simulate NVM to experiment on the YCSB benchmark,and compares NVRC with the traditional WAL(Write Ahead Log)and the NVM-oriented logging scheme PCMLx(PCMLoggingx).The results show that the number of NVM writes of NVRC is 54%and 17%less than that of WAL and PCMLx respectively,and the update performance improves by 59%and 10%respectively.