I posted the original as a question re: how to import massive amounts of offline media from DVDs. No one seemed to have an answer, so:
After some messing about, this is the solution that works for me:
From Library, select "Import..."
Insert DVD containing images.
When it appears in the Source column, select it and check "Include Subfolders."
Without waiting for it to create thumbnails, select "Import."
Let LR create all the thumbnails. (Get up, stretch your legs, get coffee, make a phonecall, write checks, etc...)
Use ctrl A to select all images.
In Metadata window, type the Disk ID in the Sublocation field. Press Enter
"Set Metadata on Multiple Photos" will appear. Click on "Apply to Selected."
You will now have a way to back track to the disk where any image resides.
I find it easiest to add keywords immediately after changing the sublocation.
Hope you find this useful!