I'm far from an expert but that is a very interesting proposition Ludwig and should work. The last time I had an experience similar to what you describe (placing a new drive in beside one containing data) I found the TwinStore active with heaps of flashing, for many days. And that involved only 1000 or so albums for a 2 TB HDD. I suspect a full quota of 4000+ would take up to a week to settle down - quite a bit longer than a backup. However once drive 2 had been copied the incremental backup, changes should be similar to those with an external drive and not take very long.

About the only possible hiccup I can see would be if you deleted albums. That could confuse the system as I have been told by my dealer such changes are not registered in backups. So, although the main TwinStore drive (call it no 1) would register the new library with some deleted, No 2 would still have those albums on file.

Experts - please comment.

John