Towards Read-Intensive Key-Value Stores with Tidal Structure Based on LSM-Tree

Abstract

Key-value store has played a critical role in many large-scale data storage applications. The log-structured merge-tree (LSM-tree) based key-value store achieves excellent performance on write-intensive workloads which is mainly benefited from the mechanism of converting a batch of random writes into sequential writes. However, LSM-tree doesn’t improve a lot in read-intensive workloads which takes a higher latency. The main reason lies in the hierarchical search mechanism in LSM-tree structure. The key challenge is how to propose new strategies based on the existing LSM-tree structure to improve read efficiency and reduce read amplifications.This paper proposes Tidal-tree, a novel data structure where data flows inside LSM-tree like Tidal waves. Tidal-tree targets at improving read efficiency in read-intensive workloads. Tidal-tree allows frequently accessed files at the bottom of LSM-tree to move to higher positions, thereby reducing read latency. Tidal-tree also makes LSM-tree into a variable shape to cater for different characteristic workloads. To evaluate the performance of Tidal-tree, we conduct a series of experiments using standard benchmarks from YCSB. The experimental results show that Tidal-tree can significantly improve read efficiency and reduce read amplifications compared with representative schemes.