Apple posted a minor update to Xsan for Snow Leopard today, version 2.2.2. From the release notes:

The Xsan 2.2.2 Filesystem Update is recommended for all Mac OS X v10.6 Snow Leopard-based Xsan 2.2 systems. This update improves general file system reliability and

improves file system reliability when the filesystem is highly fragmented

improves file system reliability when unmounting a volume

improves file system reliability when running snfsdefrag

improves file system reliability when native extended attributes are enabled

improves Finder reliability when browsing a volume that is highly fragmented

allows Xsan Admin to create new volumes when more than 100 fsm processes are running

The compatibility matrices for Xsan, StorNext, and Grass Valley K2 MDCs have also been updated to reference the update.

Xsan 2.3 remains a Lion exclusive.