What is an acceptable level of hard write errors on tape? Specifically, what is acceptable on HP LTO-2 media? Is it a hard number of errors, a ratio of hours in use to errors, or something else entirely?
We are using a MSL6000 library with one LTO-2 drive using Backup Exec 11d (for now). Backup Exec always shows some soft errors for most of the drives, but some are starting to show hard errors. Backups are done with immediate verification, and the verify has yet to fail, so I don't have reason to be alarmed right now.
While I can find the duty cycle for the drive (250,000 hrs), I can't seem to find any hard numbers as to when a particular tape should be should just be retired.
If there's a best practice for rotating media out, I'd love to hear that, too. We're also soon migrating to LTO-4 media, so thoughts on errors there would also be helpful.
Edited to add:
I don't have hard error on every tape. To give an idea of what I'm looking at:
Tape Hours in Use Hard Errors A 142 11 B 255 0 C 159 2
The vast majority of my tapes are like B and C. A is the outlier.
I'm looking for some sort of best practice here. The tapes are verifying OK. I don't want to have a tape fail just when I want to restore, but I also don't want to toss a tape with a handful of errors if it's unnecessary.