Thomas,
It appears that there is no free documentation that is still available.
If you have login access to SunSolve, then the Sun System Handbook has document links within the array references.
By example, in the SSA102 resource link in the Handbook, the User Guide and the Installation guide both seem to state that so long as the storage peripheral passes its own mini-POST, then what you see are the last four characters of the WWN (World Wide Name).
Perhaps others can jump in here, particularly if I'm mistaken.