Comment 6 for bug 1718212

Unfortunately there is no easy way to calculate the "reserved" disk space, i.e. the non-OpenStack usage. In the VMware case this is not a static value, especially if you are using a shared datastore for both OpenStack and non-OpenStack workloads.

We may try to report the used disk space as "reserved" but I am not sure what kind of implications that would have. IMO, calculating the resource usage in Nova instead of using the data returned by the hypervisor is poor design choice.

Jay, as a workaround you may try setting "reserved_host_disk_mb" in nova.conf.