Where can I find MTTF data and repair profiles for tape libraries -- Overland in particular? Unfortunately, I haven't seen a "one-stop" comparison for libraries in quite some time, so the only real resource would be to examine each of the product's specification sheets and perform the comparison that way. But you may want to consider at a little more than just the MTTF/MTBF.
Regardless of the "time to fail", if a failure does occur, you may want to focus a little more on the time it takes to get back up and running.
According to Michael Peterson of Strategic Research Corporation, "MTBF ratings for tape libraries are no longer a true measurement of reliability when building mission-critical capable network storage solutions. The proof of reliability comes with the supplier's reputation, warranty, and service policies. If you accept the fact that failures happen, the true measurement of reliability is system availability."