diff --git a/cinder/volume/drivers/rbd.py b/cinder/volume/drivers/rbd.py
index ef702f027dc..82964e3c629 100644
--- a/cinder/volume/drivers/rbd.py
+++ b/cinder/volume/drivers/rbd.py
@@ -360,6 +360,10 @@ class RBDDriver(driver.CloneableImageVD,
             ports.append(port)
         return hosts, ports
 
+    def _iterate_cb(self, offset, length, exists):
+        if exists:
+            self._total_usage += length
+
     def _get_usage_info(self):
         with RADOSClient(self) as client:
             for t in self.RBDProxy().list(client.ioctx):
@@ -368,7 +372,7 @@ class RBDDriver(driver.CloneableImageVD,
                     # non-default volume_name_template settings.  Template
                     # must start with "volume".
                     with RBDVolumeProxy(self, t, read_only=True) as v:
-                        self._total_usage += v.size()
+                        v.diff_iterate(0, v.size(), None, self._iterate_cb)
 
     def _update_volume_stats(self):
         stats = {