Welcome to the #StorageMinute series where we deliver key topics via bite-size content. In this edition, we will take a look at Virtual Volumes (vVols) and UNMAP.
Recently I’ve had a few conversations on vVols and UNMAP asking whether UNMAP works with vVols and if so how. The short answer is yes Trim/UNMAP work very well with vVols.
With traditional storage, VMFS or NFS, when a supported VM and GOS issue Trim or UNMAP, the command is passed through the vSphere storage stack and then passed to the array. With vSphere 6.7, space reclamation further matured enabling configurable UNMAP and support for SESparse disks. The new features in vSphere 6.7 only apply to VMFS and NFS and not vVols. This is because the vVols disks are directly mapped to the VM. This allows the GOS to pass the Trim/UNMAP commands directly to the array bypassing the vSphere storage stack. As a result, the space reclamation operation is more efficient with vVols.
You can see in the image, with VMFS datastore the Space Reclamation options are available.
You can see from this image there is no Space Reclamations option available for a vVols datastore.
In the video, you will see the deletions of data and running the optimize tool manually to speed the reclamation process. Then after some time, the disk size on the VM will be reduced and the space on the array is also reduced. The time it takes to reclaim the space varies and is dependent on the array.
A few key points:
- Not all arrays support Trim/UNMAP on vVols, check with your array vendor to verify.
- Because the array is handling the space reclamation, it may not be immediate. Some arrays may wait for a certain amount of time to reclama the space allowing for recovery of accidental deletions.
- You must have VM HW version 11 or higher for Windows and 13 or higher for Linux.
References:
KB Article: How Virtual Volumes and UNMAP primitive interact? (2112333)
https://kb.vmware.com/s/article/2112333?lang=en_US
VMworld Session: Better Storage Utilization With Space Reclamation UNAMP HCI3331BU with John Nicolson and Jason Massae.
https://storagehub.vmware.com/t/vsphere-storage/vmworld-2/better-storage-utilization-with-space-reclamation-unmap-hci3331bu/
Cody Hosterman’ s blog on vVols and UNMAP
https://www.codyhosterman.com/2018/03/vmware-capacity-reporting-part-v-vvols-and-unmap/
