Performance Analysis and Optimization of the Hurricane File System ...

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CHAPTER 2. BACKGROUND AND RELATED WORK 13 script, has an exclusive home directory and executes shell commands independent of other users. Throughput is measured in terms of scripts per hour. Although it can be used to measure file system scalability, it is not specifically a file system benchmark but more of a general system scalability benchmark. Chen and Patterson [15] have found that SDET spends less than 25% of the time doing I/O, making it unsuitable for our use. PostMark [30] emphasizes access to many small, short-lived files that all need equally fast access. In particular, it simulates a mail or network news server workload. It uses only 4 simple operations: (1) create file, (2) delete file, (3) read entire file, and (4) write to end of file. A specified number of random operations are executed and statistics are gathered. PostMark uses a single working directory and does not create and exercise a directory hierarchy. The applicability of benchmark performance to real-world workload performance is a much debated issue. Some researchers claim that previous file system benchmarks are inadequate in reflecting real-world workloads and contain various inadequacies [15, 16, 72, 69]. Chen and Patterson [15, 16] developed a technique of measuring a few basic file system operations and projecting performance based on the characteristics of the proposed real-world workload. They also address the problem of scaling a benchmark appropriately to suit the target platform. Smith [72] developed a benchmarking methodology that predicts file system performance for a specific workload and aids in bottleneck identification. Smith and Seltzer [71] advocate the need to age a file system before taking measurements in order to provide a more realistic file system state. They use a simulated workload to age the file system. In summary, many researchers are not satisfied with the currently available file system benchmarks. Some are out-dated and no longer applicable. Some do not stress the I/O system adequately because they are not file system bound. In this thesis, we use custom benchmarks that are designed to stress specific components of the file system. A custom macrobenchmark is used for the sole purpose of verifying that the custom microbenchmark performance results were applicable at some level of generality. We will show that improving the performance scalability of fundamental file system operations leads to scalability of the file system in general.
Chapter 3 HFS Architecture This chapter describes the various components of HFS and their interactions with the operating system and user-level applications. The organization and operation of the cache systems within HFS are described in detail because they play a crucial role in file system performance scalability, since they are globally accessible to all processors and are the most used components of the file system. Traces of a few fundamental file system operations are described to demonstrate the interaction between the cache system and the on-disk layout of data and meta-data. This chapter will give the reader an understanding of the operation of HFS, the interaction of various components, and the potential scalability bottlenecks. 3.1 HFS Layers The components of HFS are shown in Figure 3.1. Communication between domains (i.e. address spaces such as application, HFS, and kernel) is accomplished using the K42 IPC facility. HFS can be accessed directly using the HFS user-level library, or indirectly through the virtual file system of the operating system kernel using standard I/O system calls. Currently, only the indirect access method has been implemented. Additional details of the HFS architecture can be found in [34]. 3.1.1 HFS User-Level Library The HFS user-level library, also known as the Alloc Stream Facility (ASF) [36], is an application level interface to general I/O, which includes HFS, NFS, and other file systems. It is in the form of a user-level library, much like stdio.h in the standard C library. The HFS library has not been ported to K42, but its functionality has been partially fulfilled by the standard Unix/Linux/GNU C library and the K42 user-level library. 14
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Chapter 7 Macrobenchmark 7.1 Purpos
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CHAPTER 7. MACROBENCHMARK 68 server
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CHAPTER 7. MACROBENCHMARK 70 avg #
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CHAPTER 7. MACROBENCHMARK 72 Logica
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CHAPTER 7. MACROBENCHMARK 78 7.5 Ot
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CHAPTER 7. MACROBENCHMARK 80 to deq
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CHAPTER 8. CONCLUSIONS 82 8.1 Gener
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CHAPTER 8. CONCLUSIONS 84 read-only
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Bibliography [1] Gene M. Amdahl. Va
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BIBLIOGRAPHY 88 [33] David Kotz, So
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BIBLIOGRAPHY 90 [71] Keith A. Smith
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