I did this as an inhouse backup for a data warehousing app.
Just slapping 4 ide cards into a case and putting 16x250gb IDE drives on them resulted in a system that would copy about 1 disk worth before hanging with some fault or suddenly dropping to 1% speed.
Just because you can in theory hook 40 drives to n cards doesn't mean it will work - well done to them
Just because you can in theory hook 40 drives to n cards doesn't mean it will work - well done to them