I have found that the latest version of the Dell MD Storage has ODX on by default. When using the storage migration with this turned on the VHDX files transfer instantly between the LUN's but the VHDX is corrupt and causes the Virtual Server to blue screen and then to never boot again. I have yet to find a way to recover any data.
My current work around is to disable ODX on the array itself which means that the data is transferred by the hosts, but does not corrupt the VHDX files.
show storageArray odxsetting;
set storageArray odxEnabled=false;