Research On New Indexing Technologies For Non-Volatile Memory

In recent years,powered by storage technology developing,a new non-volatile Memory(NVM)based on 3D Crosspoint technology is beginning to be commercial-ized,which further promotes the research of NVM oriented database system.As a completely novel memory tier between DRAM and SSD,persistent memory provides new opportunities and changes for the improvement of index designing.Focusing on the access characteristics of NVM,this paper studies the new index-ing technology for NVM,and focuses on the performance optimization of the access,persistence,range query and other operations of tree index on NVM.Through the de-sign and optimization of index architecture,memory structure,and the corresponding index operation algorithm adjustment and optimization,the index can give full play to the performance of NVM and hybrid memory architecture.In general,the main work and contributions of this paper can be summarized as the following aspects:(1)A new NVM-based hybrid index named HARTCombining the characteristics of B+tree and Radix tree,this paper proposes a two-layer hybrid index named HART.Considering that searching in B+tree is relatively slower,while queries in Radix tree is faster,we redesigned the architecture and improved the strategy of path compression.To solve the problem of the poor range query of Radix tree,and the scattered data storage,we proposed a write-efficient node for NVM to store old leaves,with linked at the bottom of the tree.(2)Optimization strategies and concurrency control methods for HART in hybrid memory architecture Since NVM as a memory tier between DRAM and SSD,index on hybrid architecture can be more efficient than on NVM-only architecture.Therefore,in order to minimize NVM writes,We propose a strategy to separate the boundary of heterogeneous index model from the persistent boundary,and further discuss the con-current access control strategy of the lower persistence layer.Based on the design and implementation of the technical scheme,experiments are carried out on simulation and real persistent memory system.We compared the perfor-mance of different derived variants of HART and other indexes of NVM types under different key distributions.The experimental results show that HART is more affected by key distribution than other Radix tree indexes,and the range query performance is similar to that of B+tree indexes.The read and write performance has an advantage in the case of locally dense keys.In the case of completely uniform and sparse distribu-tion,the write performance is equivalent to that of NVM-only indexes,while the read performance is significantly better than other indexes.