The problems you are trying to solve with backup are backup window issues, and recovery point and recovery time objective issues. Do I have the flexibility to be able to recover from different points, and how quickly can I get that data back when I want to restore it? And then reliability.
In the archive arena, t's a lot more important to deal with things like the cost of storage over time. That cost has to be much lower because your archives are going to be storing a lot more data. If I archived something five years ago and then I go to get it, how do I know for sure that what I'm getting back actually is a reliable representation of what that data looked like when I first put it in the archive?
But there's a third requirement making companies start to consider active archival storage platforms – in other words, disk-based platforms – a lot more seriously, and that is the requirement for online searchability. A lot of companies are spending a lot more to run e-discovery against tape-based archives than they would against disk.
Many companies are making the assumption that each lawsuit is going to cost them $500,000 in e-discovery costs if they're running against tape-based archives. If it's costing you $500,000 per lawsuit to handle e-discovery efforts against tape, it doesn't take very many lawsuits to get disks to be competitive with tape.
A lot of companies are still looking at backup and archive as the same thing, the only difference that that the archive tapes happen to be sitting at an offsite location. The e-discovery aspect needs to be taken into account.