Yeah, you do have to trade off performance, safety and price, and that 
depends.  With an unlimited budget (hah!), a need to maximize performance and 
an utter lack of fear of losing data, a SCSI RAID-0 arrangement would make 
the most sense.  

But lose the unlimited budget, and the increasingly good performance (and 
much better prices) of IDE drives starts to complicate matters.   The last 
time I looked, you could put together an 90-or-so gig SCSI RAID-0 package for 
something like ten grand (using 18 9-gig RAID hard drives, which seemed to 
have the best price point per megabyte at the time, at about $50 per gig.  
Plus, of course the cost of the controllers.  RAID controllers aren't cheap.


You can buy, just to pick a decent brand, a 40-gig IBM DeskStar for  less 
than a hundred each, and do the RAID-0 array for less $200 (okay, you only 
get 80 gig instead of the ninety -- make it a three-disk array, and you're at 
120 gig for less than $300), or double up, run a RAID 0+1 array of four IBM 
60-gig drives for $600, plus a much cheaper controller.  

Will you get better performance out of the SCSI system?  Sure.  How much 
better?  I dunno.  Hell, set up a four-disk IDE RAID-system, and stripe the 
RAID-0 partition across all four, and you might well beat the SCSI system.