diff --git a/watcher/decision_engine/model/collector/nova.py b/watcher/decision_engine/model/collector/nova.py
index 3f1fd4eb5..24a7537d1 100644
--- a/watcher/decision_engine/model/collector/nova.py
+++ b/watcher/decision_engine/model/collector/nova.py
@@ -356,7 +356,12 @@ class NovaModelBuilder(base.BaseModelBuilder):
             "memory_ratio": memory_ratio,
             "memory_mb_reserved": memory_mb_reserved,
             "memory_mb_used": memory_used,
-            "disk": node.free_disk_gb,
+            # The node.free_disk_gb does not take allocation ratios used
+            # for overcommit into account so this value may be negative.
+            # We do not need this field and plan to set disk to total disk
+            # capacity and then remove disk_capacity.
+            "disk": disk_capacity,
+            # TODO(licanwei): remove and replace by disk field
             "disk_capacity": disk_capacity,
             "disk_gb_used": disk_used,
             "disk_gb_reserved": disk_gb_reserved,
diff --git a/watcher/decision_engine/model/notification/nova.py b/watcher/decision_engine/model/notification/nova.py
index 60c689d70..e5bec587e 100644
--- a/watcher/decision_engine/model/notification/nova.py
+++ b/watcher/decision_engine/model/notification/nova.py
@@ -133,7 +133,12 @@ class NovaNotification(base.NotificationEndpoint):
                 status=_node.status,
                 memory=_node.memory_mb,
                 vcpus=_node.vcpus,
-                disk=_node.free_disk_gb,
+                # The node.free_disk_gb does not take allocation ratios used
+                # for overcommit into account so this value may be negative.
+                # We do not need this field and plan to set disk to total disk
+                # capacity and then remove disk_capacity.
+                disk=_node.local_gb,
+                # TODO(licanwei): remove and replace by disk field
                 disk_capacity=_node.local_gb,
             )
             self.cluster_data_model.add_node(node)
diff --git a/watcher/tests/decision_engine/model/notification/test_nova_notifications.py b/watcher/tests/decision_engine/model/notification/test_nova_notifications.py
index 1ece440b1..593e05e07 100644
--- a/watcher/tests/decision_engine/model/notification/test_nova_notifications.py
+++ b/watcher/tests/decision_engine/model/notification/test_nova_notifications.py
@@ -313,7 +313,7 @@ class TestNovaNotifications(NotificationTestCase):
         node_2 = compute_model.get_node_by_name('Node_2')
         self.assertEqual(7777, node_2.memory)
         self.assertEqual(42, node_2.vcpus)
-        self.assertEqual(974, node_2.disk)
+        self.assertEqual(1337, node_2.disk)
         self.assertEqual(1337, node_2.disk_capacity)
 
     @mock.patch.object(nova_helper, "NovaHelper")