Add usage field
diff --git a/openstack/db/v1/instances/results.go b/openstack/db/v1/instances/results.go
index 33c68c1..ae3b9e0 100644
--- a/openstack/db/v1/instances/results.go
+++ b/openstack/db/v1/instances/results.go
@@ -20,6 +20,8 @@
 type Volume struct {
 	// The size in GB of the volume
 	Size int
+
+	Used float64
 }
 
 // Instance represents a remote MySQL instance.