Guest OS unmap not working for Windows Server VM with ReFS filesystem

Products

• VMware vSphere ESX 7.x
• VMware vSphere ESX 8.x
• VMware vSphere ESXi

Issue/Introduction

On deletion of files within a Windows Server guest from within ReFs filesystem, datastore/storage space is not reclaimed via unmap. 

Environment

VMware vSphere ESXi Storage 7.0
VMware vSphere ESXi Storage 8.0

 

Cause

Guest level unmap is supported by Microsoft on ReFS only in conjunction with Microsoft Storage Spaces. See Resilient File System (ReFS) overview. 

Resolution

Configure MS Storage spaces in conjunction with ReFS filesystem, as per Microsoft requirements.