Came across this today, if you have a VMDK file that is over 1.98TB you will not be able to create a snapshot of the server. Please see articles below.
Essentially you need to allow for a 16GB overhead so the maximum size the VMDK can be is 2032GB, 1.99TB calculates to 2037GB and 1.98TB calculates to 2027GB.
http://www.virtualtothecore.com/en/the-real-maximum-size-of-a-vmdk-file/
