Hi guys, I've found a super cool script to share with you: https://communities.vmware.com/message/2483410#2483410
The script is named vmware_unmap_datastore.ps1.zip - 3.1kbit
Be careful to run set-executionpolicy unrestricted
before starting the script and also to create a C:\Temp folder.
I'm using the script in interactive mode, it is super fast due to advanced calculation of block size to use with UNMAP command. Default esxcli command on my 1 TB LUNs took about 4 - 5 minutes, with this script just a few seconds
Be careful to point the script to you vCenter server and to have at least vSphere 5.5. The script will automagically detect thin-provisioned LUN at storage level, so don't worry if you have a mix of thin and thick LUN on different storages. It will UNMAP only thin-provisioned LUNs