We have several thin provisioned RHEL guests and supposedly storage reclamation is possible, if the file system is mounted with the discard option.
I have followed this reference
So I went on and tested this with:
First I edited /etc/lvm/lvm.conf and changed issue_discards = from 0 to 1
mount -o remount,discard,rw /opt
dd if=/dev/zero of=/opt/bigfile.dat bs=1M count=6000
fstrim -v /opt
Output: fstrim: /opt: FITRIM ioctl failed: Operation not supported
And from the VMware perspective the vmdk uses 6GB more space but does not decrease again.
Does anybody have any ideas about this?