diff --git a/aodh/storage/__init__.py b/aodh/storage/__init__.py
index 4af2b8fd0..e6d6e6895 100644
--- a/aodh/storage/__init__.py
+++ b/aodh/storage/__init__.py
@@ -22,6 +22,7 @@ from oslo_utils import timeutils
 import retrying
 import six.moves.urllib.parse as urlparse
 from stevedore import driver
+import warnings
 
 _NAMESPACE = 'aodh.storage'
 
@@ -53,6 +54,12 @@ def get_connection_from_config(conf):
     else:
         url = conf.database.alarm_connection
     connection_scheme = urlparse.urlparse(url).scheme
+    if connection_scheme not in ('mysql', 'mysql+pymysql', 'postgresql',
+                                 'sqlite'):
+        msg = ('Storage backend %s is deprecated, and all the NoSQL backends '
+               'will be removed in Aodh 4.0, please use SQL backend.' %
+               connection_scheme)
+        warnings.warn(msg)
     LOG.debug('looking for %(name)r driver in %(namespace)r',
               {'name': connection_scheme, 'namespace': _NAMESPACE})
     mgr = driver.DriverManager(_NAMESPACE, connection_scheme)