VMware ESXi: Clean up .ctk files
VM disk consolidation or Storage vMotion fails due to -CTK files.
Remove or rename any files ending with the *-ctk.vmdk file extension in the virtual machine directory.
http://paulgrevink.wordpress.com/2013/12/02/vm-disk-consolidation-fails/
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2048201