Because disk I/O has such a huge impact on system performance, file-system design and implementation command quite a lot of attention from system designers.
Some file systems are general purpose, in that they can provide reasonable performance and functionality for a wide variety of file sizes, file types, and I/O loads.
Others are optimized for specific tasks in an attempt to provide better performance in those areas than general-purpose file systems.
The write-anywhere file layout (WAFL) from Network Appliance is an example of this sort of optimization.
WAFL is a powerful, elegant file system optimized for random writes.