vSphere 5.0 Update 1 introduces a tool to manually reclaim deleted blocks
With today’s release of VMware vSphere 5.0 Update 1, included is an update to vmkfstools that enables administrators to manually reclaim deleted blocks on thin provisioned LUNs on VAAI capable storage arrays.
The new flag added to vmkfstools is “-y” and takes the percentage of the deleted blocks to reclaim as an argument.
You need to cd into the VMFS volume with the deleted blocks before you run the command.
# cd /vmfs/volumes/MyThinVol
# vmkfstools -y 70
This will reclaim 70% or the deleted blocks. Note that this works even though the UNMAP Primitive was disabled when you installed Update 1. It is time consuming though. My advice is to run this off-peak time and place the host in maintenance mode.
See VMware KB article 2014849 for details.