diskutil coreStorage in Lion fails to create a concatenated LVG, error -69886
Operating system
Can you reproduce the problem with Mac OS X 10.7.5?
If -69886 arises from a failure to unmount
Expanding upon a hint in an answer to a linked question, try this before the Core Storage operation … for the device that apparently can't be added:
diskutil unmount /dev/disk2s2
– then if the unmount fails, to discover what's open:
sudo lsof /dev/disk2s2
Reference
Currently limited by Apple to Mac OS X 10.7.4: diskutil(8) OS X Manual Page