标题: | 利用混合式快取机制提升行动档案系统之效能 Improving Mobile File System Performance with Hybrid Caching Mechanism |
作者: | 甄元彬 黄育纶 Huang, Yu-Lun 电控工程研究所 |
关键字: | 行动档案系统;快取机制;Mobile File System;Cache Mechanism |
公开日期: | 2008 |
摘要: | 档案快取机制与策略是决定分散式网路档案系统传输与存取效能的重要因素,尤 其是应用于频宽受限的行动网路档案系统中。常见的档案快取机制有全档快取 (Whole-File Cache,简称WFC)及区块档案快取(Block-File Cache,简称BFC)。其中, WFC 是一种广泛应用于分散式网路档案系统中的档案快取机制。透过WFC,使用者可 以在本机端保留档案副本,以节省再次存取相同档案时所需耗费的网路频宽与传输时 间。BFC 的运作机制则是将档案切割为许多区块,并以区块为单位,进行档案存取。 在更新档案内容时,BFC 仅需更新必要的档案区块,而不需重传整个档案内容。在档 案内容变动不多的情况下,BFC 可以有效降低档案更新所需的频宽需求与传输成本。 在这篇论文中,我们设计一个混合式的快取机制(Hybrid Caching Mechanism,简称 HCM),结合WFC 与BFC 两种快取机制, 使其能依据行动档案系统中的档案类型、大 小等特性,选择适用的档案快取机制,以提升整体行动档案系统的传输与存取效能。 本研究所提出之HCM 能有效避免重覆传送相同的档案区块,并能提供类似串流式档案 存取功能。在本研究中,我们并透过一连串的实验,分析并说明引入HCM 后档案系统 的效能改善。 File caching mechanisms are essential to the performance of network file systems, especially for mobile file systems. The file cache is a specific, reserved area of virtual storage in the range of system memory address. It operates on files or file blocks. Whole-file cache (WFC) is one of the popular file caching mechanisms used in distributed network file systems. With WFC, the file client keeps a local copy of the file obtained from the remote file server. As long as the requested file remains resident in the cache, subsequent file I/O requests are resolved directly from the cache without accessing the remote file server. Hence, the communication costs are reduced. Another file caching mechanism, block-file cache (BFC), intends to store a file in the local cache in blocks. Although more header overheads are introduced to store the block information, only dirty blocks are transmitted during updates if BFC is applied. Compared to WFC, BFC dramatically reduces communication costs if the size of dirty blocks is much smaller than the whole file. In this paper, we design a hybrid caching mechanism (HCM), combining WFC and BFC, to select a proper caching mechanism for a file according to the file type, file size, etc. After conducting a series of experiments, we show that the proposed mechanism offers a better performance than the traditional mobile file systems. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079612537 http://hdl.handle.net/11536/41853 |
显示于类别: | Thesis |
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