In my life as a consultant I seem to attract clients that need a network janitor. Regardless of whether the cause was a CIO past his prime trying to squeak out a couple last years by keeping the budget down or just a network that grew past its designer's ability, the network's not working right. I've also learned that if the network's not working right, the backup system isn't working at all. As a result, I frequently have to specify a new tape library before I have good capacity planning data. Since I have to guess at how many tape drives and slots the client will need for the next 10 (or even 2) years, I pick a modular library that can grow with the client's needs.

The Quantum PX502 and Overland NEO series are the tape library version of stackable Ethernet switches. Stack two or more library modules and you can treat them like one large library. An optional elevator unit on the Overland, or special pop-up tape slot on the PX502, moves tapes from one library to the other, letting any tape be mounted in any drive.

Need more slots, add modules without drives. Need more drives, add full libraries. Little muss, no fuss, and no forklift upgrades (assuming they don't discontinue the model you need). Now I'll never have to explain how they outgrew the tape library I had them buy 6 months ago again.

Disk to disk is great, but it requires process changes that can take years to implement and even then there's a place for tape for the long run.