title: App Engine Flexible running out of disk space
body: <p>Stopping and deleting old versions and instances in my project doesn't seem to free up disk space. After stopping and deleting a working instance and then spinning up a new instance I get error messages related to disk space (health_check returns unhealthy, i get logs of vm_check_disk_space.sh). I know this is related to disk space as I can resolve the issue by raising <code>resources: disk_size_gb</code> in my app.yaml and redeploying.</p>
  
  <p>My project is 15gb so it's essential that deleted versions and instances don't bloat my project. How can I go about freeing up unused space?</p>
  
  <p>For reference this is my app.yaml (and with a project size of 15gb this should be more than enough?)</p>
  
  <pre><code>runtime: custom
  env: flex
  
  manual_scaling:
    instances: 1
  
  resources:
   cpu: 1
   memory_gb: 1.5
   disk_size_gb: 40
  </code></pre>