Research On Technology Of Flash Memory-Based Mass Storage System

The data explosion in today's information age makes great challenges to storage system, including the challenges to the conventional file systems and the challenges to the storage devices. Fortunately, the rapid development of new storage devices makes it possible to relieve the stress of the storage system. In this paper, we make efforts to improve the overall performance of the flash-based storage system by improving the performance of file system and storage device. The main work and innovation of this paper are as follows:1. In order to meet the demand of big data processing and lower the extra consumption of flash memory caused by file system, we propose a flash-friendly hash-based indexing structure—HyEx-Hash, and a directory indexing scheme based on HyEx-Hash—HashTree. HyEx-Hash lowers the extra consumption of flash memory and HashTree improves the performance of directory indexing.2. Considering that files with different size require different amount of index, we improve the performance of file data indexing for big files and lower the extra cost to store small files by making different optimizations for files with different size.3. Based on the two optimizations above, we design and implement a new flash file system—HIFFS which uses hybrid indexing schemes. The hybrid indexing scheme is reflected in both directory indexing and file data indexing.4. SSDs in RAID system have a bigger write amplification and will be soon worn off. In order to relieve this problem, we propose a RAID-Aware SSD which could distinguish user data from parity according to the different access patterns in RAID system. RAID-Aware SSD stores parity and user data separately in different flash blocks to reduce the impact of parity updating on user data. The effort results in lower overhead of garbage collection, and an improvement of write performance and lifespan.