This article explains the way to expand the disk space of Juniper Junos Space Virtual Appliance.

While extending the disk from Junos Space console message says "No free disk Space, exit...". 

If you expand or increase the existing hard disk of the Virtual machine then "Expand VM Drive Size" will not work, user need to add another Hard Disk and then use the option to Expand from Junos Space CLI using jmp_setup utility.

As mentioned in the technical document to expand the disk space of Junos Space Virtual Appliance, you need to follow below steps:
 

1. In the VMware vSphere Client, right-click the Junos Space Virtual Appliance icon and select Power > Power On. The Junos Space Virtual Appliance must be powered on to add disk resources.
2. Right-click the Junos Space Virtual Appliance icon and select Edit Settings.

   The Virtual Machine Properties page is displayed.

3. Select and click ADD NEW DEVICE.
4. Under Disk, Drives and Storage, select Hard Disk.
5. The New Hard Disk will appear with default storage.
6. Under New Hard Disk, select increase to the recommended size for the partition that you want to expand
7. Click ok to save the settings.

https://www.juniper.net/documentation/us/en/software/junos-space23.1/junos-space-virtual-appliance-pwp/topics/task/junos-space-virtual-appliance-disk-resource-adding.html