Will VMFS unmap freed data and give back to its backed storage after deleting a large VMDK file?

[sinoleao2018]

I ask the question as I did the test below, and found no data block was not freed in lun level after deleting the VM.

if ESX host frees data block in block/LUN level when deleting VMDK file, it can help the storage utilization more efficient.
Did i miss some configuration in vsphere?

1. create a thin-provisioning LUN in my storage array. The allocated size of the new LUN is zero now.

2. mount the LUN in ESXi host as a VMFS data store.

3. create a VM with 40GB eagerly zeroed thick VMDK in the data store.

4. in vsphere UI, the used size of the data store is a little more than 40GB.

5. in the storage array management UI, the allocated size of the LUN is around 40GB.

6. delete the VM.

7. in vsphere UI, the used size of the data store is decreased to less than 1GB.

8. however, in the storage array management UI, the allocated size of the LUN is still around 40GB.

9. I looked into the metadata of the LUN, no data block was not freed in lun level after deleting the VM.

[SupreetK · Accepted solution]

1) Are you referring to automatic unmap with VMFS-6 or are you running manual unmap command?

2) Does your array even support unmap? https://cormachogan.com/2016/12/05/determining-array-supports-automated-unmap-vsphere-6-5/​ / Storage reclamation – part 1 – VMware vSphere | Kalle's playground

3) During the unmap, are you seeing an increment in the Delete Stats under VAAIStats in esxtop? VAAI Thin Provisioning Block Reclaim/UNMAP In Action - VMware vSphere Blog

Cheers,

Supreet

[sinoleao2018]

Thanks! After running manual unmap command "esxcli storage vmfs unmap -u <UUID>", the storage space was reclaimed.

Does only VMFS-6 support automatic unmap? Can I enable automatic unmap on VMFS-5?

[SupreetK]

Nope, auto-unmap is available only with VMFS-6. And only if, the storage array supports auto reclaim. Please close the thread if your queries have been answered.

Cheers,

Supreet