In a nutshell, unmap is used to reclaim storage blocks on VMFS datastores.
I was running into alerts from my DellEMC Equallogic storage stating my volumes we’re greater that 90% consumed, I should really change that to 80%.
So when I log onto the Storage Manager I see the volume as only having 281.79GB free.
Yet from the vSphere web client I can see free space of 2.01TB, a slight difference.
To get around this and reclaim the space I need to run the esxcli unmap command.
First step is to enable SSH on a host that has access to the storage volumes.
Use putty to connect to the host and run the following command to list the storage volumes
~] esxcli storage filesystem list
Next cd to the the particular mount point you require to clean up
~] cd /vmfs/volumes/xxxxxxx-xxxxx-xxxx…
Now run the below command entering the UUID of the required Volume.
~] esxcli storage vmfs unmap -u xxxxxxx-xxxxx-xxxx…
While this is running you will see no activity on the putty session but can monitor the progress from the Storage manager, this can take some time depending on space to be reclaimed, storage etc.
Resulting free space in the case is here:
This can be done on the fly with no impact.