Goodmorning,
During some test in staging environment we see that to clone a vmdk disk of 100GB, the operation take about 1,40 H. Also, the source disk is configured in Thin mode, so the real size of the data inside is approximately 30 GB. I've seen, anyway, that he copy the entire disk even the byte with 0, so I have to transfer not only the real data size but the all disk.
Is there a way to optimize this process and copy only the data part of the disk? 
Thanks in advance for your time.
Alessio