The typical consultant's answer would be: "It depends." Different manufacturers rate their tapes differently, some more optimistically than others do. Usually, the rating will vary depending on whether the tape is in use of shelved for long term retention. Some vendors also rate full passes and tape loads separately. For example:
- The IBM 3592 tape media is rated at 300 full-file passes, 40000 short length cycles, 20000 load/unload, and 30 years shelf life (under optimal conditions)
- LTO tape media is rated at 260 full-file passes, 5000 load/unload, and 30 years shelf life (under optimal conditions)
- SDLT claims 1,000,000 head pass durability and 30 years shelf life
These numbers should be used as guidelines but real life use, handling and storage conditions will prevail and life span may be much shorter than advertised. As a rule of thumb, the first time a write error occurs on a tape media, the situation should be monitored closely. If a write error reoccurs, remaining data on the tape should be migrated and the faulty media replaced. If a read error occurs on a tape media, all remaining data on the tape should be migrated immediately and the faulty media replaced.
Read Doug Owens' answer to this question.