Volume needed depends on the vacuum loss due to uncovered holes. If all vacuum holes are covered by the sheet of film, then the volume of air vacated by the pump could be small, if not, the vacuum leakage can put great demands on the vacuum pump. Back in the days using a BIG graphic arts process camera, the vacuum pump for the film back was essentially a vacuum cleaner, not silent in any way. The film back was about 36" x 36" the vacuum leaks depending on the sheet of film used.

Vacuum levels require should be modest as it does not require much vacuum to hold a sheet of film flat.