In terms of drives, you should have plenty of space, just not much available externally. Once again, I highly recommend you look at the various reseller Web sites and they'll show you EXACTLY what you can fit. If you have a high number of drives, e.g. you're running RAID 0+1 or RAID 5, then you won't be able to fit them all in a 1 or 2U. Even a 4U unit has limited space. But if you just need HDD, CD-ROM and FDD, you'll be fine.