h-Hash: A Hash Index Structure for Flash-Based Solid State Drives

Abstract

Flash-based solid state drives (SSDs) have been widely used as storage medium because of their fast access speed, high reliability and low power consumption. In spite of these advantages, they inherit distinct characteristics such as no in-place updates, asymmetric operation speed and unit because they consist of NAND flash memories. Therefore, a disk-based hash index structure may result in severe performance degradation if it is directly deployed on a NAND flash memory-based storage system. In this paper, we propose a new hybrid hash index structure for flash-based SSDs. It delays and reduces the split operations which cause slow block erasure and additional read and write operations by exploiting overflow buckets according to the ratio of updates and deletions. Through various performance evaluations, we show the superiority of our proposed index structure by comparing it to other hash index structures for flash-based SSDs.