1986 to 1993 the "Big Vax" had 32MB memory and was clustered with the 780 and the HSC disk controller via a dedicated Computer Interconnect bus. The clustered disks provided a massive 9 GB of filestore (wouldn't even keep a home PC happy these days ).
The system was shared between users by allocating budgets and charging according to a demand factor ( an idea proposed by Prof. Peter Stocker ). Demand was calculated based on a mix of cpu ,disk io & paging rates - so users working in prime time paid more for their jobs.
VMS Load Management Overview paper