Migrating thick eager/lazy Zeroed provisioned VMs from traditional SAN storage to vSAN does not result with automated change to thin provisioning.

Products

• VMware vSAN

Issue/Introduction

When migrating VMs with attached thick provisioned eager/lazy zeroed virtual disks, from traditional SAN to a vSAN datastore, the thick provisioning does not change to thin provisioning as expected for attached  VMDKs.
These VMs after the migration will  trigger the vSAN online health alarm "Thick-provisioned VMs on vSAN"

Environment

vSAN 7.0.x
vSAN 8.0x

Cause

Legacy thick provision flag in the vmdk is not recognized by vSAN, therefore the default change to thin is not performed as expected.

Resolution

To workaround this do one of the following:

• Reapply the policy on the VM
• Make a change to the policy such as enable force provisioning and then disabling it forcing vCenter/vSAN to recalculate the policy
• Clone the policy currently in use on the VM and apply the new policy, the policy can be switched back to the original if so desired.

 

 

Additional Information

For more information on migrating to vsan please see: Migrating virtual machines to vSAN from other clusters or datastores