Automatic space reclamation doesn't work on VMFS6 with unmap granularity greater than 1 MB

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• You are using thin-provisioned storage arrays with ESXi and VAAI Delete Status is supported on the Storage Array.
   
• You have set the Space reclamation priority as low.
   
• The host cannot automatically issue the T10 unmap command from VMFS6 and VM guest operating systems to reclaim unused space from the array.
   
• ESXi supports automatic storage space reclamation on VMFS6 datastores but its not working for the storage arrays with unmap granularity greater than 1 MB.

 

 

 

Environment

VMware vSphere ESXi 6.#
VMware vSphere ESXi 7.#
VMware vSphere ESXi 8.#
VMware vCenter Server 6.#
VMware vCenter Server 7.#
VMware vCenter Server 8.#

Resolution

• ESXi does not support the automatic space reclamation on arrays with unmap granularity greater than 1 MB. If the unmap granularity of the backing storage is greater than 1 MB, the unmap requests from the ESXi host are not processed.
   
• You need to verify the File Block Size on the Storage Array which should not be greater than 1 Mb.
   
• For more information on Auto Unmap feature and its limitations, see UNMAP section in vSPhere 7.0 Storage.
   
• To verify the Auto UNMAP feature support footnote for your storage, see VMware Hardware Compatibility Guide (HCL).
  
  Example:
  
  

 

Additional Information

VMFS 5 supports manual space reclamation.

 

For more information on space reclamation features, see ESXi and Array Thin Provisioning section in VMware vSphere 6.5 Documentation Center.