Exporting and importing a VM converts most disks to thin allocation

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

This article explains why an export and re-import of a VM will cause loss of disk allocation type specificity.

Symptoms:
Exporting a VM to an OVF and then importing the OVF to a new VM will usually convert the VM's disks to thin allocation type.

Environment

VMware vSphere ESXi 7.0.2
VMware vSphere ESXi 7.x
VMware vSphere ESXi 7.0.3
VMware vSphere ESXi 5.5
VMware vSphere ESXi 7.0.1
VMware vSphere ESXi 5.1
VMware vSphere ESXi 8.0.1
VMware vSphere ESXi 6.5
VMware vSphere ESXi 8.0.x
VMware vCenter Server 7.0.x
VMware vSphere ESXi 6.0
VMware vSphere ESXi 7.0
VMware vSphere ESXi 6.7
VMware vCenter Server 6.0.x
VMware vCenter Server 8.0
VMware vSphere ESXi 5.0

Cause

When you export a VM from a datastore to an OVF, the VM's disks are always converted to a specialized sparse format. It does not matter whether the disk was originally thin, thick, or eager-zeroed thick on the datastore. When you re-import the VM from the OVF back onto a datastore, the new disks will almost always appear to be of the thin allocation type. This is by design and there is no way to customize disk allocation type when importing a VM.

Resolution

Currently there is no resolution.

Workaround:
You need to inflate the new disks using UI or API commands after you have re-imported the VM to convert them to eager-zeroed thick.