1GB drives are extremely small these days. You can get USB thumbdrives larger than this.
You will need a system that will support a RAID (redundant array of inexpensive/independent disks). There are different raid types that can be implemented but with 5 drives, you should consider RAID 5. See the RAID5 section in this SearchStorage article on RAID.
There are also some considerations about dividing out the OS, page file, log files & database files. Here’s a sample of some considerations on database storage design on SQL servers.
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Is that GB a typo?
I would configure RAID 1/0 with 4 disks, and leave the 5th as a hot spare.