Adaptive, Low-Cost Garbage Collection for Durable Page-Mapping Multichannel SSDs

• Main Authors: Liu, Yu-Syun, 劉宇洵
• Other Authors: Chang, Li-Pin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/42917256671847364453

碩士 === 國立交通大學 === 資訊科學與工程研究所 === 103 === In recent years, random access memory equipped with SSDs are increasing, so there will be enough space for page-level mapping table. Page-level mapping flash translation layer can avoid the overhead caused by merge log block and data block when using hybrid-level mapping, so page-level mapping have higher write speed and lower degree of wear. But many of garbage collection policy design for page-level mapping flash translation layer, need to calculate scores for each physical block when they are selecting victims for garbage collection, or record time for each logical page when they are writing user data, or have some parameters in different situations can not automatically adapt to the optimum value, need for human setting. With solid-state hard disk capacity increases, these kind of approach become infeasible in terms of time or space overhead. Dual-greedy proposed improvements for these problems, records block level information, reduce the cost of random access memory space. Time complexity of Dual-greedy is constant, and all parameters can automatically adjust to the best state in run time, without artificially setting. But Dual-greedy dose not consider the wear-leveling problem, and it's performance will decreases when implementing on multichannel architecture. Therefore, We propose an new page-level mapping flash translation, the methods of garbage collection policy is based on Dual Greedy, but improment performance for multi-channel architecture, and consider the problem of wear-leveling, make SSDs more duable. This study have three parts. The first is to improve the Dual-greedy in a multi-channel architecture, solve the problem that the efficiency of garbage collection policy of Dual-greedy decreases when the number of blocks within a single channel becomes less. The second is using simple data structures, fast and effective balance each physical block erase count in a channel. And the third is for a multi-channel architecture with dynamic binding, balance the degree of wear for every channel, let the remaining life of each channel is consistent, extend the overall life of SSDs.