I have a Kubernetes node with a small root disk and a large disk plumbed into /var/lib/docker

Kubernetes does GC on disk images when the used space reaches X%. Whats it looking at though? I can't find it in the docs.

Just to clarify, if you've got / with 20GB of space and /var/lib/docker with a second disk of 100GB, if K8S looks a / the % free is much less, potentially than /var/lib/docker, but / doesn't change much where as the mapped in drive, does.