Required drive speed depends a bunch on the type of video editing you're doing. For example, native DV editing can require far less drive speed than near lossless mpeg compression rates.(posted 9208 days ago)Some dv systems can get away with a striped drive set of Ultra DMA EIDE drives and the Promise Fastrack controller. I have a DV Master Pro system that never drops frames using a single Seagate Barracuda (7,200rpm) LVE drive connected to an Adaptec 2940U2W controller. It has to handle something like 3-5mb/sec I think; I forget the exact transfer requirements of DV. The audio and system drive is an EIDE Seagate Medalist drive.
On the other extreme, my main editing system that uses a Digisuite LE, runs on striped sets of 3 Barracudas (U2W SCSI drives & controller) for video. I capture at anywhere between 7 and 15mb/sec on that card... not counting the data rates required for layering those video clips during editing. The entire system (including CD reader/writer) is SCSI, which gives better performance than a mix of SCSI and E/IDE drives.
You'll notice that in both systems I chose the Barracuda drives over Cheetahs. I had a few dealers report that the Cheetahs tended to run hot, and I wanted to avoid the headaches associated with that--heat management is tough enough with just 'cuda drives.
Personally, I'd definately recommend investing in the Adaptec 2940U2W controller and LVE capable drives (LW serial # extension on Seagates). Ultra 2 Wide SCSI is not only faster, but also supports longer cable lengths (short's always better though) and tends to be less finicky in general.
As for reliability, I have a total of 9 Barracuda drives now (7 nine- gig drives and 2 eighteen-gig drive) between the two systems. Over the past 6 months I haven't had a single problem with any of them.
Hope that was useful, -- John P.S. I'm assuming you're looking at PC based systems. If you're considering building a mac based NLE system on the new G3 machines you may want to avoid SCSI for video drives. I've read some discussions on the DV email list about problems with SCSI speeds on those machines. I didn't pay a lot of attention to that discussion thread though, so if it applies to you then I'd check it out yourself.