With version 6 I backup my sytem partition daily to 2 separate locations a NAS drive and an external USB drive eg NAS at midday, USB at 5pm

How does the CBT function work in such a situation? Can it track the changes so it works with both locations at once?

Thanks

My guess is that the CBT driver makes "checkpoint" records when each backup is captured.  So for example let's say you capture Backup A-1 to Location A, and then you capture Backup B-1 to Location B.  When you try to capture Backup A-2 to Location A, Reflect can query the CBT driver to say, "Tell me everything that has changed since Backup A-1" rather than just, "Tell me everything that has changed since the last backup that was captured anywhere," because obviously the latter wouldn't allow CBT to work in your scenario.  But whatever the technical details are, it does actually work.  I use a daily disk rotation and CBT works fine with all of those disks as long as the most recent backup on a the current target disk was captured in the current Windows session, which it usually was since this strategy is used with a server that doesn't get restarted very often.

Thanks for that - so long as it works that's fine by me