Our field engineers get asked some tough questions. A common one is: "how do I change my backup product from vendor X to vendor Y?" This is a surprisingly rich topic of discussion. It turns out that making this change is definitely possible, but it's not easy. There are a few reasons why:
We tend to keep backup data around for a very long time.
There's no standard tape format – regardless of what vendors call their formats.
Vendors don't publicly document their tape formats, and those formats change over time.
Every backup tool is configured and managed differently than every other product.
Backup products are extremely complex.
Reading that list should make the answer almost self evident. I'm going to spoil my own ending and tell you the answer first. You don't swap out; you transition.
Why do I say that? Let me tell you a little history. I'm primarily a NetBackup guy. Back in the stone age of NetBackup, I managed a group of folks who trained customers on NetBackup. We could confidently say that after a week-long course, the administrators were capable backup admins with NetBackup. We could present all of the features of the product, provide best practices, and sprinkle in lab time to re-enforce the concepts. We even had time to take people out to nice lunches. Nowadays, delivering the same level of training would require a minimum of three to four weeks. Perhaps even longer. And it's not just NetBackup. The same could be said about CommVault, NetWorker, TSM (it would need months), and any of the enterprise-class products. I don't really care what the vendors say about their ease of use, there's just too much to learn. Transitioning from one product to another requires extensive retraining. That training is both technical and operational. Because each product approaches backups differently, the nature of how you define your policies often has to be rethought. Those changes then have to be communicated to your organization's stakeholders – and approved by them. What's worse, the administrators charged with doing this change have to pull double duty for the duration of this project. You simply cannot change from one tool to another over night. Not in any reasonably sized environment.
Does that mean it's not possible? Certainly not. Lots of companies have changed from one product to another and done it successfully. It's just a ton of work – usually more than what's expected.
Once you change products, you have the issues of your legacy and its retention. You see, we keep our data for a long time. Most of our customers have retentions measured in years, in decades, or even infinite retentions. That one always gets me. I'd like to see someone recover a tape written today in 30 years. I'd really like to see them do it in 100 (as in I hope I'm still alive then to laugh at them). Besides the practical issues regarding obsolete technology, there's the fact that the data itself and the backup product used will be in formats that aren't easily recognizable. (Side note: Think about it this way... I have WordStar files from my early CP/M days that I can still read because I just keep moving my data from one computer to the next, but I have nothing that reads WordStar documents natively any more. Those brilliant middle school essays of mine are mercifully lost to history.)
Anyway, the point is that we have a ton of data that we keep for a long time just in case we need to recover it. The "simple" answer is to convert the data from one backup product to another, right? Wrong. There's no magical easy button for this. Again, each backup product writes their data differently. Some backup products can convert the catalog or index of what's on each piece of media for you, but none of them can read the tape formats of another vendor. On occasion, we've been asked to convert the data for a customer. That involves using the old software and restoring each and every piece of media to a temporary location. Then that location is backed up by the new backup tool.
Those are very expensive projects. We'll be happy to do them. You won't be happy to pay for them.
And it's getting worse. We regularly deal with customers that have tens of petabytes of data now. It won't be long before we're dealing with customers with exabytes. Recovering and re-backing up that volume of information will simply not work.
The "easy" answer is that you don't retire the old backup product until you either expire all of the data that was under its control or you get the volume of data down to a reasonable level for the conversion.
To sum it up, converting backup products is hard, but doable. Don't expect to move your data from one vendor to another unless you want to spend a ton of money on professional services. It's far simpler to keep the old system around for legacy restores and start fresh with the new one.