Space reclamation of VMFS 5 Datastores using esxcli

Space reclamation of VMFS 5 Datastores using esxcli

It was a bit quiet here in January caused by a new “private project” which has attracted some resources, and will pull more resources in the future.
But this will not stop me from documenting useful stuff. This one is nothing new, but commonly asked by some customers: How do I get my storage capacity back after deleting VMs?!
The outlined steps are all done using esxcli. You need to execute them on a single ESXi host, not on each host in the cluster.


Connect to one of your ESXi hosts using SSH. You can use this small PowerCLI command to enable SSH on a specific host.

Get-VMHost esx1.lab.local | Get-VMHostService | Where Key -EQ "TSM-SSH" | Start-VMHostService

The first step is to identify the datastore(s) from which you want to reclaim storage.

[root@esx1:~] esxcli storage vmfs extent list

Volume Name    VMFS UUID                            Extent Number  Device Name                           Partition

-------------  -----------------------------------  -------------  ------------------------------------  ---------

VMDS01         55dc0522-c72eebec-3780-d89d672d7a3c              0  naa.60030d90eca17602ce5c5a54a083e31c          1

We will need the device name, and later the UUID. The next step is to identify if the device is detected as a thin-provisioned disk, and if it is VAAI-capable. I’ve shortened the output of the esxcli output to the necessary output.

[root@esx1:~] esxcli storage core device list -d naa.60030d90eca17602ce5c5a54a083e31c

    Thin Provisioning Status: yes

    VAAI Status: supported

No we have to verify if all necessary VAAI options are supported.

[root@rzb-esx-1:~] esxcli storage core device vaai status get -d naa.60030d90eca17602ce5c5a54a083e31c

naa.60030d90eca17602ce5c5a54a083e31c

    VAAI Plugin Name:

    ATS Status: supported

    Clone Status: supported

    Zero Status: supported

    Delete Status: supported

Important for us is the “Delete” primitive. If this is supported, we can use UNMAP to reclaim storage.

[root@rzb-esx-1:~] esxcli storage vmfs unmap -u 55dc0522-c72eebec-3780-d89d672d7a3c

This process will take some time depending on the amount of storage that has to be reclaimed. And it will put some load on your storage, so you might want to run this in a less productive time.