Dynamic Extent-Based Allocation Technique for Multimedia File Systems

This thesis investigates the efficiency of extent-based allocator design to satisfy file allocation requests in a CDN proxy cache. The allocator is based on the method inspired by the memory allocators, where free space is managed in chunks of varying size, or extents. The design is tested in a simulation, where a trace of allocation and deallocation events from a content server was submitted to the allocator. The bottleneck for content retrieval often lies on data transfer rates of the hard disks used in the server. To facilitate fastest possible transfer of a file, it must be read sequentially. At the same time, given the large quantity of files, space wastage due to incomplete utilisation of large allocation units is not desirable. Our allocator design tries to achieve both mutually exclusive goals. The design was implemented and the results we obtained in the course of simulation, show that we managed to achieve these goals, creating an allocator that displays properties, favourable for contiguous file placement, while keeping space wastage at its minimum.