How to resolve the backup error 'Source and destination disk size doesn't match'

How to resolve the backup error 'Source and destination disk size doesn't match'

Introduction

Running a VMware backup job, you may face a backup job failure with the following error message:

Source and destination disk size doesn't match.

The root cause of this issue is that on the VM (Virtual Machine) the source VMDK (Virtual Machine Disk) is not an exact multiple of 1K in size or the disk has an odd number of sectors.

The VMware UI (User Interface) does not allow you to create a disk that isn't an exact multiple of 1K, but a disk that wasn't created in the UI can easily be created like this. Some ways this can happen include:

  • VMDK is created from the command line.

  • The VM was imported from Open Virtualization Format (OVF or OVA).

  • The VM was converted from another hypervisor.

  • The VM was created as part of converting a physical machine (P2V).

In order to resolve this issue, it is necessary to resize the disk to be an even number of sectors. The easy way to do this is to grow the disk from the VMware UI. Even the smallest amount the UI will allow to grow the disk will be enough.

Instructions

1) Run VMware vCenter and find the VM in the vCenter UI.
2) Right-click on the VM in question and select Edit Settings.
3) Find the Hard Disks section and check if there is a disk that isn't shown as a whole number.


4) Grow the disk to the whole number.


Once disk size is adjusted, the issue should be resolved. Initiate a Full backup job for this VM to confirm that this error doesn't occur anymore.