The XSAN filesystem is Apples version of a file system that can be used in a SAN environment. It is apparently based off ADIC StorNext product before. While the idea of a SAN filesystem is typically used in an enterprise environment for storage consolidation, the fact that one has a single storage back end that is accessible in the same way from any node make the same idea good for clusters. However, there are many ways that this can be achieved. Sometimes, via NFS, SAN or Parallel File systems.
XSan Filesystem – The original document form TWiki
Performance Tuning on SNFS
There is quite a fair bit of information in the StorNext file system tuning guide which can be useful. It is attached below for reference.