Modern databases typically makes use of the Log Structured Merge-Tree for organizing data in indexes, which is a kind of disk-based data structure. It was proposed to efficiently handle frequent update queries (also called update intensive workloads) databases. In recent years, LSM-Tree has gained popularity and has been adopted by a number of NoSql databases, and key-value stores. Since LSM-Tree was first proposed, researchers and the database community started efforts to improve different components of LSM-Tree. In recent years, Non-volatile Memory, also called Persistent Memory, has also gained significant popularity. This is a class of memory that is non-volatile and byte-addressable at the same time, and hence also termed Storage Class Memory. Apart from that, storage class memory exhibits the combination of the best characteristics of both memory and storage. An overview of the current state of the art in LSM-Tree-based indexes, data systems, and Key-Value stores is provided in this paper.

翻译：现代数据库通常采用日志结构合并树（LSM-Tree）这种基于磁盘的数据结构来组织索引中的数据。该结构最初为高效处理频繁更新查询（即更新密集型负载）而提出。近年来，LSM-Tree日益普及，已被众多NoSQL数据库和键值存储系统采用。自LSM-Tree首次提出以来，研究人员和数据库社区持续致力于改进其各组件。而近年来，非易失性存储器（也称持久性内存）同样获得了显著关注。这类存储器兼具非易失性与字节可寻址特性，因而也被称为存储级内存。此外，存储级内存融合了内存与存储介质的双重最佳特性。本文对当前基于LSM-Tree的索引、数据系统及键值存储领域的最新研究进展进行了全面综述。