Availability and locality measurements of peer-to-peer file systems

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Abstract
Although peer-to-peer networking applications continue to increase in popularity, there have been few measurement studies of their performance. We present the first study of the locality of files stored and transferred among peers in Napster and Gnutella over month-long periods. Our analysis indicates that the locality of files is skewed in all four cases and fits well to a log-quadratic distribution. This predicts that caches of the most popular songs would increase performance of the system. We also took baseline measurements of file types and sizes for comparison over time with future studies. Not surprisingly, audio files are most popular, however a significant fraction of stored data is occupied by videos. Finally, we measured the distribution of time peers in Gnutella were available for downloading. We found that node availability is strongly influenced by time-of-day effects, and that most user's tend to be available for only very short contiguous lengths of time.
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