MPSearch: Multi-Path Search for Tree-based Indexes to Exploit Internal Parallelism of Flash SSDs

Big data real-time processing aims for faster retrieval of data and analysis. Lately, in order to accelerate real-time processing, big data platforms are trying to exploit NAND flash based storage devices, especially SSDs. NoSQL DBMSs have been used for real-time management of big data which significantly depends on index structures to efficiently manage data. Previous research about flash-aware index structures addressed the potential problems of hard-disk oriented designs. In this paper, we focus on exploiting potential benefits of flash SSDs. First, we examine the internal parallelism of flash SSDs by benchmarking several flash SSDs. Then we present a new I/O request concept, called psync I/O, that can exploit the internal parallelism of flash SSDs in a single process, and we propose a new search method (MPSearch) that enables tree based indexs to exploit the internal parallelism of flash SSDs. Based on MPSearch, we present a B+-tree variant, PIO B-tree (Parallel I/O B-tree). PIO B-tree enhanced B+trees insert performance by a factor of up to 16.3, while improving point-search performance by a factor of 1.2. The range search of PIO B-tree was up to 5 times faster than that of the B+-tree. Moreover, PIO B-tree outperformed other flash-aware indexes in various synthetic workloads. In order to enhance NoSQL DBMS performance on flash SSDs, PIO B-tree can be adopted or MPSearch can be applied to other tree-based index structures adopted in NoSQL DBMSs.