Panorama PAN-OS 12.1 upgrade fails, ‘no enough disk space to hold image’

In getting ready to move Panorama to PAN-OS 12.1 from 11.1 (to manage some new PA-5×0 series firewalls) if you haven’t already performed the ‘224GB’ disk size increase you are likely to bump into this error message:

Successfully downloaded
Software version: 12.1.2
Preloading into software manager
Failed to create required free space. Free space: 3191 MB, Required space: 3717 MB
No enough disk space to hold image
Failed to load into software manager. Please retry.
Post processing failed. Please retry.

After a little chuckle at the error in the error message (No != Not) the fix is simple, swap out the Panorama OS disk with a larger one following the exact steps of the guide below.

https://docs.paloaltonetworks.com/panorama/11-1/panorama-admin/set-up-panorama/set-up-the-panorama-virtual-appliance/increase-the-system-disk-on-the-panorama-virtual-appliance/increase-the-system-disk-for-panorama-on-an-esxi-server