I'm not sure I understand the question, but it sounds to me like you want to have a spare machine available for restoring data if the E450 fails. Don't plan on simply copying the backup files from one machine to another. If you really want to be clean about this with the least possible problems you should consider buying additional software for the Sparc 20. I know it seems like a waste of time, but you don't want to find yourself with a stupid licensing problem keeping you from restoring data. By all means test this scenario and do not go on "good faith."
Also make sure you verify that you can redirect the restore operation from the Sparc 20 system to whatever server you will restore data to. This can be the Sparc 20, but the restore is still a redirection operation. I don't know the details of Solstice backup, but typically the backup software is smart enough to know the machine ID and volumes that it was backed up from and a normal restore will want to put it back in the same place - not necessarily the same relative position on one of the mounted volumes. So you need to be aware of the command syntax or other interface operations needed to ensure the restore will work as planned.
Obviously, you need the correct device controllers in the Sparc 20 that are compatible with the tape equipment you have in the E450.
One more thing, make sure you think about how system security or metadata may or may not be restored. Again, I don't know the details of Solstice backup, but if the restore occurs on a machine that is used for other purposes, you want to make sure the system software configuration doesn't get screwed up.
Hope this helps.
This was first published in April 2001