Ideally, you don't want to have to manage your keys. So when we talk about key management, you want this to be as automated as possible. You are counting on an application to do this for you and you don't want to have to copy it anywhere.
For example, a backup product like Tivoli Storage Manager is fully integrated with IBM's LTO-4, so the backup product would take care of key management. This is an ideal set up because you don't want to have to worry about another component taking care of your keys.
Again, one of the main drawbacks to encryption is losing your keys, so you want to back that up. And as simple as this may sound, you don't want to back up your key to encrypted media. You want to make sure you backup your keys and keep your keys somewhere where you can retrieve them. In the Sun STK offering, their station that takes care of key management is capable of replicating it to another one. So, it is also good to do this and ensure you always have a set of keys that is available to you.
Check out the entire Tape Encryption FAQ.