diff --git a/src/charm.py b/src/charm.py
index caf195e..894b996 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -14,6 +14,7 @@ from ops.framework import (
     StoredState,
 )
 from ops.main import main
+import ops.model
 import charmhelpers.core.host as ch_host
 import charmhelpers.core.templating as ch_templating
 import interface_ceph_client
@@ -98,6 +99,9 @@ class CephISCSIGatewayCharmBase(ops_openstack.OSBaseCharm):
 
     DEFAULT_TARGET = "iqn.2003-01.com.ubuntu.iscsi-gw:iscsi-igw"
     REQUIRED_RELATIONS = ['ceph-client', 'cluster']
+    # Two has been tested before is probably fine too but needs
+    # validating
+    ALLOWED_UNIT_COUNTS = [2]
 
     def __init__(self, framework, key):
         super().__init__(framework, key)
@@ -287,6 +291,13 @@ class CephISCSIGatewayCharmBase(ops_openstack.OSBaseCharm):
         self.state.enable_tls = True
         self.on_pools_available(event)
 
+    def custom_status_check(self):
+        if self.peers.unit_count not in self.ALLOWED_UNIT_COUNTS:
+            self.unit.status = ops.model.BlockedStatus(
+                '{} is an invalid unit count'.format(self.peers.unit_count))
+            return False
+        return True
+
 
 @ops_openstack.charm_class
 class CephISCSIGatewayCharmJewel(CephISCSIGatewayCharmBase):
diff --git a/src/interface_ceph_iscsi_peer.py b/src/interface_ceph_iscsi_peer.py
index ca156f3..0d2067c 100644
--- a/src/interface_ceph_iscsi_peer.py
+++ b/src/interface_ceph_iscsi_peer.py
@@ -100,3 +100,12 @@ class CephISCSIGatewayPeers(Object):
         for u in self.peer_rel.units:
             addresses.append(self.peer_rel.data[u]['ingress-address'])
         return sorted(addresses)
+
+    @property
+    def peer_count(self):
+        return len(self.peer_rel.units)
+
+    @property
+    def unit_count(self):
+        return len(self.peer_rel.units) + 1
+
diff --git a/tests/bundles/focal.yaml b/tests/bundles/focal.yaml
index 19b7281..2d0cac8 100644
--- a/tests/bundles/focal.yaml
+++ b/tests/bundles/focal.yaml
@@ -1,14 +1,31 @@
-series: bionic
+series: focal
+machines:
+  '0':
+    constraints: mem=3072M
+  '1':
+  '2':
+  '3':
+  '4':
+  '5':
+  '6':
+    series: bionic
+  '7':
+    series: bionic
+  '8':
 applications:
   ubuntu:
     charm: cs:ubuntu
     num_units: 1
+    to:
+      - '8'
   ceph-iscsi:
     charm: ../../
-    series: focal
     num_units: 2
     options:
       rbd-metadata-pool: tmbtil
+    to:
+      - '0'
+      - '1'
   ceph-osd:
     charm: cs:~gnuoy/ceph-osd-5
     num_units: 3
@@ -16,23 +33,35 @@ applications:
       osd-devices: 'cinder,10G'
     options:
       osd-devices: '/dev/test-non-existent'
-      source: cloud:bionic-train
+    to:
+      - '0'
+      - '1'
+      - '2'
   ceph-mon:
     charm: cs:~gnuoy/ceph-mon-6
     num_units: 3
     options:
       monitor-count: '3'
-      source: cloud:bionic-train
+    to:
+      - '3'
+      - '4'
+      - '5'
   vault:
+    series: bionic
     num_units: 1
 #    charm: cs:~openstack-charmers-next/vault
     charm: cs:~gnuoy/vault-29
+    to:
+      - '6'
   mysql:
+    series: bionic
     charm: cs:~openstack-charmers-next/percona-cluster
     num_units: 1
     options:
       innodb-buffer-pool-size: 256M
       max-connections: 1000
+    to:
+      - '7'
 relations:
 - - ceph-mon:client
   - ceph-iscsi:ceph-client