Which HD
I'll tell you which hard drive I reccomend at the end.
First of all, regarding backup. I have racked my brain for quite some time trying to figure out the best backup strategy for GB's upon GB's of data. I have yet to really hear a great solution. The best solution that I have heard yet...and the approach I will be taking will be just keep buying IDE drives. At $200 each for 45GB drives (see below), why bother backing it up other than for reliability? Just pull out the drive, label it, put it in a static-free bag and on a shelf and put a new IDE drive in. You can fit a couple hours of music on a single IDE drive in multi-tracks. Years ago I used to have to plop down $45 for 30 minutes worth of 16 track half inch tape.
If you want secondary copies of the music, I'm still trying to find the right solution. Tape backup solutions are expensive when you start talking about many GB's of data. DVD-RAM is expensive for the Media. CDR would take forever and a year to backup a project. I might also start buying inexpensive, but slower IDE drives to backup to. You can probably put an entire CD project (all track data) onto a $50 IDE drive I would bet.
Second of all, why do you want to use Firewire for your drives? They are hotswappable, which is cool....but you'll be paying more money for that luxury.
Are you Mac or PC? On my PC, I use an IDE swappable drive bay. I do have to powerdown my PC, but I can plop in a new IDE drive in just a few minutes. Its literally only seconds if I have the other HD already in a swap bay cartridge. The swap bays go for about $50 and the extra cartridges are between $10-$20. I would imagine that this would work just as well with a Mac that has an IDE interface installed.
I've also seen (can't remember names right now) Firewire cases which you simply plop in any IDE drive you want and the case interfaces with Firewire. If you really want Firewire, I would reccomend this solution, since IDE drives are by far the least expensive and they are getting PLENTY fast.
As to which drive, the consensus right now seems to be that the IBM Deskstar 75GXP is the one to get in the IDE world for audio/video applications. It sports 37MB/sec sustained transfer rate (I've produced 35MB/sec sustained on my PC), ATA100 for data bursts, and its VERY quiet. I can hardly hear mine. No clicking ever. It uses some kind of new ceramic spindle thing that IBM has created to keep it quiet. AND, it can take up to 400 G's of shock when not in operation. When in operation it can still take up to 50 G's.
I bought my audio PC from
http://www.soundchaser.com and this is the drive that they have chosen as the best drive for audio data. In particular, they've come to the conclusion that the 45GB size gives the most GB's per dollar. It comes in various different sizes, but I own 2 45GB drives of this model.
The 45GB version can be found for $200.
Here's a link about it
http://www.storage.ibm.com/hardsoft/diskdrdl/desk/ds75gxp.htm
To make matters more interesting though, IBM just barely announced a new drive...that sounds even nicer. They are claiming 40 MB/sec sustained data transfer from this one and other things.
http://www.storage.ibm.com/press/hdd/desk/20001114.htm