Reclaiming space in VMware is an annoying thing.
But with a little help from VMware's community it can be a much simpler process.
I saw a recent comment in an old Thread and thought it would be a good idea to finally post this.
I found the attached script here: https://communities.vmware.com/message/2437373
Here's what the script does after you pointed it to vCenter:
1) Get a list of all datastores and loop through them.
2) Find out how much space is free and calculate 0,5% of that.
This is something you can tune in line 144. (I've never touched it)
[decimal]$freeDSSpace = $ds.FreeSpaceMB
$unmapSize = [MATH]::round($freeDSSpace*.005)
3) Run the vmfs unmap
I've been using this Script for the past year and gave it to most of my customer.
Never saw any problems with it.