Originally PMed by: mechBgon
Congratulations on the new position! I'm tempted to say you should try to wriggle out of being the guy left holding the bag on that decision. You know that the minute anything were to go wrong... yeah. You get the blame.
Small picture: as a "near-line storage" solution, I suppose IDE RAID1 could be ok. I would do a software mirror in Windows Disk Management on the two drives, and make their partitions about 5% smaller than their full capacity just so you would have an easy time repairing the mirror later when a drive fails, even if the new drive is slightly lower in capacity than the dead one.
One of the nice things about software mirroring is that if half of the mirror goes down, the other half ought to be recoverable to any computer, it has nothing to do with any specific RAID card or controller. Just check on the mirror every week or less to ensure it's still alive, and give the drives forced-air cooling to ensure they stay nice and comfy As for drives, I would probably use Seagate 7200.7's if the usage is going to be as light as it sounds.
Anyway, the software RAID1 is what we do at work, with SCSI drives in our case. It's saved our bacon on our older server once... when one drive failed, we bought a new pair of drives, restored the mirror with one of the two, then replaced the surviving old drive with another new one and restored the mirror again. Piece of cake
Big picture: If it were me, I would probably recommend a pair of 73GB Seagate Cheetah 10k.6 or 10k.7's and move ALL of your data files to them after they pass about a week of burn-in. If your 18GB SCSI drives are as old as the P3-powered server, then I would start being a little leery of putting my eggs in their basket, so to speak. Use 'em in RAID1 for just the OS, and put your data on the 73GB SCSI RAID1.
At Newegg, 73GB Cheetah 10k.7's are US$290. So maybe $800-$1000 Canadian for a pair of them. If you have a fan-cooled hot-swap backplane thingie like you described, you can simply plop them in the caddies (80-pin SCA2) and not have to get a new controller, cable or terminator.
For a backup solution, if you want to do USB then you should consider whether the server will take a USB 2.0 card, or any USB card. If it's WinNT 4.0 Server, then AFAIK USB is a pure impossibility because the OS can't do it. If it's got USB 1.1 onboard, remember how slow that's going to be, backing up ~20GB of data at 1MB/sec. Ouch.
At any rate, remember that choosing the SCSI drive(s) doesn't necessarily rule out USB backup, but make sure USB backup is even an option, too. Since your data is your livelihood for more than a dozen people, I would go high-roller and say 80GB Quantum DLT1 SCSI tape drive and software, ten tapes and a cleaning tape, and have three Friday tapes in rotation, two of which are at the bank in a safe-deposit box. It's data insurance, just like you guys undoubtedly carry other types of insurance too. Amortize it over five years and call it a business expense and write it off
Hope those random mumblings help with the brainstorming.