This is a slightly weird problem.
My setup is basically this:
iMac with Internal HD
Physical External Drive 1 (CrossFire) is an External Drive with two partitions used for keeping work
Physical External Drive 2 (LaCie) is a Second External Drive with six partitions, one of which is used for Time Machine backup.
Having heard that Time Machine doesn't always restore a disk as identical (I gather it is a bit clever at missing out some root level stuff?), as well as Time Machine backups, I clone my main drives once a month on their respective opposite partitions on the Time Machine physical disk. In other words my physical backup drive has everything backed up in both Time Machine and clone format - the best of all worlds. It also enables me to boot from the backup drive in the event of an Internal HD failure.
Attached is a basic diagram of the drive and partition layout.
So far I've been using Time Machine to only backup my Internal Drive on my iMac. However I want to add one of the partitions from CrossFire so that it too gets backed up on Time Machine (see the red line on the diagram).
My problem is this:
When I add the external drive I want to backup it all works perfectly and Time Machine is flawless. But if I disconnect that drive (CF-2) and the clone of that drive (LC-2) is still connected, when Time Machine does its next backup, it thinks the clone of that drive (LC-2) is actually the drive I want backed up (CF-2) and merrily copies all 100gb of data, even though the clone is on a different partition of a different physical drive and has a different disk name. If I look in the "Exclude Items" list, with the drive I want backed up connected (CF-2), the clone (LC-2) is listed as needing to be excluded, but when the drive I want backed up is disconnected, the clone of it disappears from the "Exclude" list. In other words the external drive I want to be Time Machine backed up pulls its opposite clone in and out of the "Exclude" list as it gets mounted and unmounted. And no amount of going in and adding the clone to the "Exclude" list will make that setting stick.
How do I convince Time Machine to ignore the clone and only work with the original?
Is there some identification tag that Time Machine uses (rather than simply the disk name) which fools it into thinking that the clone is the original?
And if so, how do I override it?
As ever, any thoughts or advice most gratefully received.