diff --git a/README.rst b/README.rst
index 7ea6da8..0943db2 100644
--- a/README.rst
+++ b/README.rst
@@ -298,6 +298,15 @@
           # Add key without value to remove line from policy.json
           'compute:create:attach_network':
 
+Configure host_subset_size
+--------------------------
+
+.. code-block:: yaml
+
+    nova:
+      controller:
+        host_subset_size: 1
+
 
 Compute nodes
 -------------
diff --git a/nova/files/newton/nova-controller.conf.Debian b/nova/files/newton/nova-controller.conf.Debian
index 0b037df..f95e6bf 100644
--- a/nova/files/newton/nova-controller.conf.Debian
+++ b/nova/files/newton/nova-controller.conf.Debian
@@ -56,7 +56,7 @@
 enabled_apis = osapi_compute,metadata
 image_service=nova.image.glance.GlanceImageService
 until_refresh=0
-scheduler_host_subset_size=30
+scheduler_host_subset_size = {{ controller.get('host_subset_size', '1') }}
 my_ip={{ controller.bind.private_address }}
 fping_path=/usr/bin/fping
 
diff --git a/nova/files/newton/nova-controller.conf.RedHat b/nova/files/newton/nova-controller.conf.RedHat
index c3b92c3..d7ce085 100644
--- a/nova/files/newton/nova-controller.conf.RedHat
+++ b/nova/files/newton/nova-controller.conf.RedHat
@@ -45,7 +45,7 @@
 enabled_apis = osapi_compute,metadata
 image_service=nova.image.glance.GlanceImageService
 until_refresh=0
-scheduler_host_subset_size=30
+scheduler_host_subset_size = {{ controller.get('host_subset_size', '1') }}
 my_ip={{ controller.bind.private_address }}
 fping_path=/usr/bin/fping
 
diff --git a/nova/files/pike/nova-controller.conf.Debian b/nova/files/pike/nova-controller.conf.Debian
index d2d7693..a95b8d2 100644
--- a/nova/files/pike/nova-controller.conf.Debian
+++ b/nova/files/pike/nova-controller.conf.Debian
@@ -4733,7 +4733,7 @@
 # Minimum value: 1
 # Deprecated group/name - [DEFAULT]/scheduler_host_subset_size
 #host_subset_size=1
-host_subset_size=30
+host_subset_size = {{ controller.get('host_subset_size', '1') }}
 
 #
 # The number of instances that can be actively performing IO on a host.
diff --git a/nova/files/queens/nova-controller.conf.Debian b/nova/files/queens/nova-controller.conf.Debian
index 17d0c4f..07b676c 100644
--- a/nova/files/queens/nova-controller.conf.Debian
+++ b/nova/files/queens/nova-controller.conf.Debian
@@ -4676,7 +4676,7 @@
 #  (integer value)
 # Minimum value: 1
 # Deprecated group/name - [DEFAULT]/scheduler_host_subset_size
-host_subset_size = 30
+host_subset_size = {{ controller.get('host_subset_size', '1') }}
 
 #
 # The number of instances that can be actively performing IO on a