- class InstanceLocalityFilter¶
Schedule volume on the same host as a given instance.
This filter enables selection of a storage back-end located on the host where the instance’s hypervisor is running. This provides data locality: the instance and the volume are located on the same physical machine.
In order to work:
The Extended Server Attributes extension needs to be active in Nova (this is by default), so that the ‘OS-EXT-SRV-ATTR:host’ property is returned when requesting instance info.
Either an account with privileged rights for Nova must be configured in Cinder configuration (configure a keystone authentication plugin in the [nova] section), or the user making the call needs to have sufficient rights (see ‘extended_server_attributes’ in Nova policy).
- backend_passes(backend_state, filter_properties)¶
Return True if the HostState passes the filter, otherwise False.
Override this in a subclass.