In Xsan Admin you can easily label LUNs that are available on your Fibre Channel fabric. Using the cvlabel command, you can also easily label a LUN that isn’t on a Fibre Channel fabric. Labeling a LUN writes data to the LUN, thus allowing Xsan to somewhat mark its territory (insert vivid imagery of an Xsan shaped like a dog taking a whiz on a poor thumb drive). If you then look at that LUN from a Mac OS X system without Xsan installed, the computer will have greyed out options in Disk Utility and will not be able to treat the LUN as a “disk.” You also can’t use…