ESXi Reclaim raw storage from thin provisioned storage

This is to reclaim raw storage after having shrunk back thin provisioned volumes.

(Example, you migrate a VM to a new datastore, leaving an empty datastore in VMWare but still containing allocated space on the SAN)

ESXi 5.0-5.1

vmkfstools -y percentage_of_deleted_blocks_to_reclaim

I usually do 98 so:
vmkfstools -y 98

ESXi 5.5

esxcli storage vmfs unmap -l MyDatastore

-l is identifying the datastore by label, you enter the name, and away it goes.

ESXi 6.5

In 6.5 as long as your datastore is V6 it will unmap slowly in the background automatically. For legacy datastores, you will still manually have to initiate it.
Source:
http://vsphere-land.com/news/automatic-space-reclamation-unmap-is-back-in-vsphere-6-5.html