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

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are out-dated and no longer applicable.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.