This article describes the Xsan 2.2.1 Filesystem Update, available as a manual download from Apple Support Downloads and as an automatic Software Update. There are two separate Xsan 2.2.1 Filesystem Updates, one for Mac OS X v10.5 Leopard and one for Mac OS X v10.6 Snow Leopard. Xsan Admin 2.2 should be used with Xsan 2.2.1.
Important: Read before installing
Be sure that all Metadata Controllers (MDCs) are updated before you make any configuration changes.
Your MDCs must always have software versions (both Xsan and Mac OS X) that are the same or more recent than the most recent client versions. For details, see this article.
During installation, do not change any Xsan settings, whether using Xsan Admin or a command-line tool.
Mac OS X or Mac OS X Server v10.5.8 or v10.6, or later (Mac OS X Server required for MDC if you are using Xsan to manage users and groups)
Xserve with an Intel processor, or Mac Pro
2GB RAM for Xsan client
2GB RAM plus 2GB per volume for MDC
Apple Fibre Channel Card
Software Update installation
Software Update may have referred you to this article. Because some updates are prerequisites for others, you may need to use Software Update more than once to get all available updates.