LSM-based Storage Techniques: A Survey

Recently, the Log-Structured Merge-tree (LSM-tree) has been widely adopted for use in the storage layer of modern NoSQL systems. Because of this, there have been a large number of research efforts, from both the database community and the operating systems community, that try to improve various aspects of LSM-trees. In this paper, we provide a survey of recent research efforts on LSM-trees so that readers can learn the state-of-the-art in LSM-based storage techniques. We provide a general taxonomy to classify the literature of LSM-trees, survey the efforts in detail, and discuss their strengths and trade-offs. We further survey several representative LSM-based open-source NoSQL systems and discuss some potential future research directions resulting from the survey.Comment: This is a pre-print of an article published in VLDB Journal. The final authenticated version is available online at: https://doi.org/10.1007/s00778-019-00555-

A Practical Concurrent Index for Solid-State Drives

Solid-state drives are becoming a viable alternative to magnetic disks in database systems, but their performance characteristics, particularlythosecausedbytheirerase-before-writebehavior,make conventional database indexes a poor fit. There have been various proposalsofindexesspecializedforthesedevices,buttomakesuch indexespractical,wemustaddresstheissueofconcurrencycontrol. Goodconcurrency control isespeciallycriticaltoindexes onsolidstate drives, because they typically rely on batch updates, which may take long and block concurrent index accesses. We design, implement, and evaluate an index structure called FD+tree and an associated concurrency control scheme called FD+FC. Our evaluationconfirms significantperformance advantages ofour approach over less sophisticated ones, and brings out insights on data structure design and OLTPperformance tuning onsolid-state drives. Categories andSubject Descriptor