关键词: 非易失性内存, 数据库日志, 异地更新, 影子记录, 原地更新

Abstract: 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.

Key words: Database log, In-place update, Non-volatile memory, Out-place update, Shadow record