I have a client with years of images across a dozen or so large hard drives.
Long story short – after a few false starts I have taken to adding each drive of images to a Lightroom Catalog on a donated PC under Windows 7 before transferring them somehow to a Mac formatted 8TB drive (I can’t afford to tie up any of my Macs with this task and besides there seem to be some issues with copying large NTFS drives to the Mac)

Drive 1 was added to the catalog without incident, then disconnected in readiness for drive 2

Drive 2 was connected, import selected and images started to stream into the catalog.
WHOA!! wait a minute – the wonderful feature of Lightroom where offline drives and their capacity can easily be seen in the left sidebar is showing only one drive

It should be showing two drives (drive 1 should have a red light and every image and folder should have a question mark while drive 2 should have a green light)

Instead it is intermingling online and offline folders. A little experimenting shows that renaming the drives (they are both My Passport drives – of different capacity) does not help

I suspect that connecting all the drives at once would work, but that’s a lot of spaghetti (12+ drives)
I also suspect that connecting all 12 drives one at a time would have every drive intermingled within lightroom

Changing the drive letter and starting again seems to solve the issue. I just have to remember to choose a different letter for each drive

This is crazy – how are normal people supposed to deal with these types of issues?
(the Mac has always been able to distinguish between even identical drives)

Still, I’m sure the problem doesn’t exist in Windows 8