Apple has posted a tutorial for configuring MultiSAN (with pictures!).Apple has posted a tutorial for configuring MultiSAN (with pictures!).
The tutorial has even solved one of confounding questions of our time, "What is MultiSAN?" To quote from the article:
What is MultiSAN? MultiSAN is a configuration in which any given MDC may host Xsan volumes that are not necessarily hosted by other MDCs.
So Volume 1 is hosted by MDC-A and MDC-B, and Volume 2 is hosted by MDC-C and MDC-D.
For the record, I'll quibble with one detail in the article:
Fibre channel switch: All MDCs, Xsan clients and storage devices should be configured to communicate in the same hard zone or orphan zone or should not reside in zone.
I think that Bulletproof Zoning, will still work, where all the storage is in a single alias. The important detail to note is that you can't zone out some of the storage from some of the clients with MultiSAN, — every client and MDC must see all the storage. But the clients shouldn't need to see each other.