ADSM is too expensive
1992: 1 GB SCSI drive DM 2800,- 200 MB Tape 3480 DM 10,-- relative cost of backup: 3.5%
1998: 18 GB SCSI drive DM 1939,-- 10 GB Tape 3590 DM 100,-- relative cost of backup: 9,2% 10 GB IDE drive DM 519,-- relative cost of backup: 19.3% and the cheap drives do need backup! Universities have many cheap drives.