| Summary: | 碩士 === 國立交通大學 === 電機與控制工程系所 === 97 === 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.
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