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The Log-structured File System (LFS), introduced in 1991 [8], has received much attention for its potential order-of-magnitude improvement in file system performance. Early research results [9] showed that small file performance could scale with processor speed and that cleaning costs could be kept low, allowing LFS to write at an effective bandwidth of 62 to 83% of the maximum. Later work showed that the presence of synchronous disk operations could degrade performance by as much as 62% and that cleaning overhead could become prohibitive in transaction processing workloads, reducing performance by as much as 40%[10]. The same work showed that the addition of clustered reads and writes in the Berkeley Fast File System [6](FFS) made it competitive with LFS in large-file handling and software development environments as approximated by the Andrew benchmark [4].

These seemingly inconsistent results have caused confusion in the file system research community. This paper presents a detailed performance comparison of the 4.4 BSD Log-structured File System and the 4.4 BSD Fast File System. Ignoring cleaner overhead, our results show that the order-of-magnitude improvement in performance claimed for LFS applies only to meta-data intensive activities, specifically the creation of files one-kilobyte or less and deletion of files 64 kilobytes or less.