Most big companies I know of are backing up to tape, but no one is using
internal tape backup drives.
Internal drives are limited to single tapes, and therefore cannot backup more than one tape's worth of data before someone's got to walk over to the machine and manually replace tapes.
In most cases (including my own) people use an external drive library with a number of drives in a box with a larger number of tapes, using some kind of robotic device to automatically swap tapes into tape drives as the backup progresses - for example if you want to backup 1TB of data onto tapes that can store 100GB each, the tape library fills up one tape, then automatically ejects the tape and loads a new one, backs up another 100GB, then repeats until all the data is backed up.
Due to the mechanics of running this, you
cannot fit this within an internal drive bay in a server, so it's enclosed in a separate, external box, typically connected via SCSI or Fiber Channel to the host computer.
No one I know of is using an
internal tape drive for any significant volume of backup.
If you want some ideas of external backup devices, check out places like:
Overland Storage
ADIC
StorageTek
and others, all of which provide both single-drive/single tape, and library/autoloader options.
