diff --git a/tricircle/cinder_apigw/controllers/volume.py b/tricircle/cinder_apigw/controllers/volume.py
index b94dc34f..d8d15912 100644
--- a/tricircle/cinder_apigw/controllers/volume.py
+++ b/tricircle/cinder_apigw/controllers/volume.py
@@ -52,13 +52,10 @@ class VolumeController(rest.RestController):
             pecan.abort(400, _('Volume not found in request body'))
             return
 
-        if 'availability_zone' not in kw['volume']:
-            pecan.abort(400, _('Availability zone not set in request'))
-            return
-
+        az = kw['volume'].get('availability_zone', '')
         pod, pod_az = az_ag.get_pod_by_az_tenant(
             context,
-            az_name=kw['volume']['availability_zone'],
+            az_name=az,
             tenant_id=self.tenant_id)
         if not pod:
             pecan.abort(500, _('Pod not configured or scheduling failure'))
diff --git a/tricircle/common/az_ag.py b/tricircle/common/az_ag.py
index a738eb71..8cabd23a 100644
--- a/tricircle/common/az_ag.py
+++ b/tricircle/common/az_ag.py
@@ -120,14 +120,27 @@ def get_pod_by_az_tenant(context, az_name, tenant_id):
         pod = core.get_resource(context,
                                 models.Pod,
                                 pod_b['pod_id'])
-        if pod['az_name'] == az_name:
+        if az_name and pod['az_name'] == az_name:
             return pod, pod['pod_az_name']
+        elif az_name == '' and pod['az_name'] != '':
+            # if the az_name is not specified, a defult bottom
+            # pod will be selected
+            return pod, pod['pod_az_name']
+        else:
+            pass
 
     # TODO(joehuang): schedule one dynamically in the future
-    filters = [{'key': 'az_name', 'comparator': 'eq', 'value': az_name}]
+    if az_name != '':
+        filters = [{'key': 'az_name', 'comparator': 'eq', 'value': az_name}]
+    else:
+        filters = None
+
+    # if az_name is valid, select a pod under this az_name
+    # if az_name is '', select the first valid bottom pod.
+    # change to dynamic schedluing in the future
     pods = db_api.list_pods(context, filters=filters)
     for pod in pods:
-        if pod['pod_name'] != '':
+        if pod['pod_name'] != '' and pod['az_name'] != '':
             try:
                 with context.session.begin():
                     core.create_resource(
diff --git a/tricircle/tests/functional/cinder_apigw/controllers/test_volume.py b/tricircle/tests/functional/cinder_apigw/controllers/test_volume.py
index 30ede022..7d9e687a 100644
--- a/tricircle/tests/functional/cinder_apigw/controllers/test_volume.py
+++ b/tricircle/tests/functional/cinder_apigw/controllers/test_volume.py
@@ -255,7 +255,7 @@ class TestVolumeController(CinderVolumeFunctionalTest):
                     "project_id": 'my_tenant_id',
                     "metadata": {}
                 },
-                "expected_error": 400
+                "expected_error": 202
             },
 
             # incorrect AZ parameter
@@ -575,7 +575,7 @@ class TestVolumeController(CinderVolumeFunctionalTest):
             elif test_vol.get('volume_xxx'):
                 response = self.app.post_json(
                     '/v2/' + tenant_id + '/volumes',
-                    dict(volume=test_vol['volume_xxx']),
+                    dict(volume_xxx=test_vol['volume_xxx']),
                     expect_errors=True)
             else:
                 return