Of course you could do that. However, my concern would be whether this is 
really necessary.

Considering disks to be 'short-term' backup media the question is how long and 
how much data has to be stored on disk at all. 
We are backing up about 120TB/month to 2 DD880s. Retention of these backups is 
1 month. After that, all data is gone.

To provide some type of 'versioning' we also clone the fulls created during the 
first 8 days/month ... on tape (ret = 18months).

Unless the retention policy of your DD save sets is significantly longer than 1 
month (which IMHO is not a good idea), the effort does not rectify the result.
I would just add the new DD and set the volumes on the old one to read-only and 
let them expire.

Of course, if you really use a DD as 'long-term' storage, then you might not 
have a choice.

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