Forgive me, I do not know much about RAID so I'm going to be
as detailed as possible.

This morning, our server's alarm was going. I found that one
of our drives have failed. (we have 3)

It is an Adaptec ATA RAID 2400A controller

I'm purchasing a new SCSI drive today. My questions:

Does the new drive have to be the same size (18 gig) as
all the others?

Can I just run the raid config utility when the new goes in?
(is that all i need to do?)

Thanks!

All drives in a raid 5 should generally be identical and must be identical in size. I don't know what an adaptec controller is, but when you replace the drive, you must rebuild the lost info. I would expect any utility to lead you in that direction. A backup would be wise.

Thank you ...

I wound up finding a couple of these drives on ebay. im glad i didn't
stick another drive in.

Bad thing is that my tape drive isnt working now and I can't understand
or bridge the problem to the drives.

I'm going to ftp a back up to our offsite server.

Thanks!