How do I view the disk usage of each virtual server?

How do I view the disk usage of each virtual server? If I go to List Virtual Servers, it does not have a disk usage or quote column.

If I go to User Interface Settings in the module config, both Disk quota and Quota used are checked to display.

If I go to Webmin -> System -> Disk Quotas, it says “User and group quotas inactive” and so I click Enable Quotas, but it still says “User and group quotas inactive” and Enable Quotas, so I dont think thats worked.

So cant see where or how to view disk usage and quotas.

Thanks

In order to enable quotas I have to run this:
ln -s /dev/xvda /dev/root

But then quotas still dont show on the “List Virtual Servers” page even though I have chosen to show them in the columns in the module Configuration -> User Interface Settings.