What were the design trade-offs made that resulted in
the specific
choices for VMS? Process scheduling? I/O? etc.
Is there a good book on this subject?
There are quite a few, depending on which version of VMS you're
interested in. Ruth Goldenberg was the author or a co-author
on most of the VMS internals books I've seen. A good place to
start is a search for anything she's written.
BLS