Instrumental CEO Henry Newman writes that tape migration is something you ignore at your own peril. He says that while migration used to be pretty straightforward, there are many reasons why this is no longer the case.
For the most part, I rely on what a former mentor referred to as EJ (engineering judgment). I generally try to complete the migration within one year of starting, 18 months at the latest. I try to ramp up the number of tape drives and storage, starting with just a few and buying more every few months following the usual price drop of both tapes and drives, trying to time the price drops based on historical data. Tapes are generally the highest-priced item in a large archive (e.g., 50,000 tapes at $85 average price is more than $4.2 million), so waiting as long as possible can provide a large cost savings. Tape migration is not easy and it is costly, however, waiting until the tapes and hardware reach end of life is even more costly and it puts your data at risk. Do not wait till it is too late.