If you have ever tried to move a volume out off a storage device and had it stall (just sit there at say 20% for hours), it could be an incorrect kernel flag. This can happen if the volume is being replicated, and basically it means that the kernel is still being replicated, so the page cannot be moved.
The solution is to reboot the array. Hoepfully though you can get all your other volumes off the array first minimizing the impact, then reboot the array and all should be fine.
This will be fixed in an upcoming firmware update.