LTO 5 tape rotation best practices - Lifetime

Tapes intended for long term archive (over a year) should be used as few times as possible before going into that archive. Fresh tapes are much more likely to last the full 30 years than a tape that was pounded weekly for a year before getting put into the Annual Archive set.

But I think you're asking about service-life for actively used tapes.

A LOT of it depends on how your tape drives work during operation. The following factors will limit service-life:

• How many full-tape accesses happen.
• The speed that the tapes are written to.
  • If the backup speed is very stuttery, the drive will stop and start a lot, and may have to shift to different throughput rates a lot. This puts a lot of stress on the media.
  • If the backup speed is constant (say, streaming directly from the backup-to-disk set as part of a media rotation scheme), they'll last longer.
• Mount count plays a role here, though that's less important than the previous point.
• Environmental factors.
  • Store them in a climate-controlled room, even the offline archives.
  • Allow the media to acclimate before use if they're coming from a space with different temp/humidity settings.

Unfortunately there is no algebraic formula to figure out chance of tape failure based on numbers of things. You'll have to build a heuristic based on your own backup patterns.

My rule of thumb is to let my backup software tell me when to replace a tape in any of the regularly-used pools. All good software does verification passes and/or checks the status of each write block with the drive. For example, when my bacula shows me a line in bconsole's list volumes output that says, eg,

|      46 | A00035L5   | Error     |       1 | 1,746,844,710,912 |    1,761 |    1,209,600 |       1 |    6 |         1 | LTO-5     | 2015-09-08 00:26:24 |

I know it's time to replace that volume.