My referenced files are organized by “Year/Month” of the date shot.
I installed a new, larger volume to store all my referenced RAW images. I did that by
- copying the images from the “DATA” to the “NEW” volume using OSX copy
- renaming the “DATA” to “OLD”
- renaming the “NEW” volume to the name of the current volume: “DATA”

Result: Aperture points to the volume “OLD”. All images have the “Offline” indicator set.
I now have to do “locate referenced files” per project and manually correct the link. I tried to do that for all files using a smart folder. That did not work (maybe all files have to be in the same OSX folder).

Lesson learned: I recommend to move the referenced file to a new volume using Aperture “Relocate referenced file”. This way AP is in the loop.