diff --git a/releasenotes/notes/host-maintenance-strategy-41f640927948fb56.yaml b/releasenotes/notes/host-maintenance-strategy-41f640927948fb56.yaml
new file mode 100644
index 000000000..3131db9fa
--- /dev/null
+++ b/releasenotes/notes/host-maintenance-strategy-41f640927948fb56.yaml
@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Added a strategy for one compute node maintenance,
+    without having the user's application been interrupted.
+    If given one backup node, the strategy will firstly
+    migrate all instances from the maintenance node to
+    the backup node. If the backup node is not provided,
+    it will migrate all instances, relying on nova-scheduler.
diff --git a/setup.cfg b/setup.cfg
index 51424727d..7239c2293 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -58,6 +58,7 @@ watcher_goals =
     noisy_neighbor = watcher.decision_engine.goal.goals:NoisyNeighborOptimization
     saving_energy = watcher.decision_engine.goal.goals:SavingEnergy
     hardware_maintenance = watcher.decision_engine.goal.goals:HardwareMaintenance
+    cluster_maintaining = watcher.decision_engine.goal.goals:ClusterMaintaining
 
 watcher_scoring_engines =
     dummy_scorer = watcher.decision_engine.scoring.dummy_scorer:DummyScorer
@@ -80,6 +81,7 @@ watcher_strategies =
     noisy_neighbor = watcher.decision_engine.strategy.strategies.noisy_neighbor:NoisyNeighbor
     storage_capacity_balance = watcher.decision_engine.strategy.strategies.storage_capacity_balance:StorageCapacityBalance
     zone_migration = watcher.decision_engine.strategy.strategies.zone_migration:ZoneMigration
+    host_maintenance = watcher.decision_engine.strategy.strategies.host_maintenance:HostMaintenance
 
 watcher_actions =
     migrate = watcher.applier.actions.migration:Migrate
diff --git a/watcher/decision_engine/goal/goals.py b/watcher/decision_engine/goal/goals.py
index 965d69c9e..2a8748035 100644
--- a/watcher/decision_engine/goal/goals.py
+++ b/watcher/decision_engine/goal/goals.py
@@ -241,3 +241,28 @@ class HardwareMaintenance(base.Goal):
     def get_efficacy_specification(cls):
         """The efficacy spec for the current goal"""
         return specs.HardwareMaintenance()
+
+
+class ClusterMaintaining(base.Goal):
+    """ClusterMaintenance
+
+    This goal is used to maintain compute nodes
+    without having the user's application being interrupted.
+    """
+
+    @classmethod
+    def get_name(cls):
+        return "cluster_maintaining"
+
+    @classmethod
+    def get_display_name(cls):
+        return _("Cluster Maintaining")
+
+    @classmethod
+    def get_translatable_display_name(cls):
+        return "Cluster Maintaining"
+
+    @classmethod
+    def get_efficacy_specification(cls):
+        """The efficacy spec for the current goal"""
+        return specs.Unclassified()
diff --git a/watcher/decision_engine/strategy/strategies/__init__.py b/watcher/decision_engine/strategy/strategies/__init__.py
index fc3a20c8e..c48529543 100644
--- a/watcher/decision_engine/strategy/strategies/__init__.py
+++ b/watcher/decision_engine/strategy/strategies/__init__.py
@@ -18,6 +18,7 @@ from watcher.decision_engine.strategy.strategies import actuation
 from watcher.decision_engine.strategy.strategies import basic_consolidation
 from watcher.decision_engine.strategy.strategies import dummy_strategy
 from watcher.decision_engine.strategy.strategies import dummy_with_scorer
+from watcher.decision_engine.strategy.strategies import host_maintenance
 from watcher.decision_engine.strategy.strategies import noisy_neighbor
 from watcher.decision_engine.strategy.strategies import outlet_temp_control
 from watcher.decision_engine.strategy.strategies import saving_energy
@@ -44,9 +45,10 @@ WorkloadStabilization = workload_stabilization.WorkloadStabilization
 UniformAirflow = uniform_airflow.UniformAirflow
 NoisyNeighbor = noisy_neighbor.NoisyNeighbor
 ZoneMigration = zone_migration.ZoneMigration
+HostMaintenance = host_maintenance.HostMaintenance
 
 __all__ = ("Actuator", "BasicConsolidation", "OutletTempControl",
            "DummyStrategy", "DummyWithScorer", "VMWorkloadConsolidation",
            "WorkloadBalance", "WorkloadStabilization", "UniformAirflow",
            "NoisyNeighbor", "SavingEnergy", "StorageCapacityBalance",
-           "ZoneMigration")
+           "ZoneMigration", "HostMaintenance")
diff --git a/watcher/decision_engine/strategy/strategies/base.py b/watcher/decision_engine/strategy/strategies/base.py
old mode 100644
new mode 100755
index 93f735006..cad186a3d
--- a/watcher/decision_engine/strategy/strategies/base.py
+++ b/watcher/decision_engine/strategy/strategies/base.py
@@ -471,3 +471,13 @@ class ZoneMigrationBaseStrategy(BaseStrategy):
     @classmethod
     def get_goal_name(cls):
         return "hardware_maintenance"
+
+
+@six.add_metaclass(abc.ABCMeta)
+class HostMaintenanceBaseStrategy(BaseStrategy):
+
+    REASON_FOR_MAINTAINING = 'watcher_maintaining'
+
+    @classmethod
+    def get_goal_name(cls):
+        return "cluster_maintaining"
diff --git a/watcher/decision_engine/strategy/strategies/host_maintenance.py b/watcher/decision_engine/strategy/strategies/host_maintenance.py
new file mode 100644
index 000000000..5693ac84c
--- /dev/null
+++ b/watcher/decision_engine/strategy/strategies/host_maintenance.py
@@ -0,0 +1,331 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2017 chinac.com
+#
+# Authors: suzhengwei<suzhengwei@chinac.com>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from oslo_log import log
+import six
+
+from watcher._i18n import _
+from watcher.common import exception as wexc
+from watcher.decision_engine.model import element
+from watcher.decision_engine.strategy.strategies import base
+
+LOG = log.getLogger(__name__)
+
+
+class HostMaintenance(base.HostMaintenanceBaseStrategy):
+    """[PoC]Host Maintenance
+
+    *Description*
+
+        It is a migration strategy for one compute node maintenance,
+        without having the user's application been interruptted.
+        If given one backup node, the strategy will firstly
+        migrate all instances from the maintenance node to
+        the backup node. If the backup node is not provided,
+        it will migrate all instances, relying on nova-scheduler.
+
+    *Requirements*
+
+        * You must have at least 2 physical compute nodes to run this strategy.
+
+    *Limitations*
+
+       - This is a proof of concept that is not meant to be used in production
+       - It migrates all instances from one host to other hosts. It's better to
+         execute such strategy when load is not heavy, and use this algorithm
+         with `ONESHOT` audit.
+       - It assume that cold and live migrations are possible
+    """
+
+    INSTANCE_MIGRATION = "migrate"
+    CHANGE_NOVA_SERVICE_STATE = "change_nova_service_state"
+    REASON_FOR_DISABLE = 'watcher_disabled'
+
+    def __init__(self, config, osc=None):
+        super(HostMaintenance, self).__init__(config, osc)
+
+    @classmethod
+    def get_name(cls):
+        return "host_maintenance"
+
+    @classmethod
+    def get_display_name(cls):
+        return _("Host Maintenance Strategy")
+
+    @classmethod
+    def get_translatable_display_name(cls):
+        return "Host Maintenance Strategy"
+
+    @classmethod
+    def get_schema(cls):
+        return {
+            "properties": {
+                "maintenance_node": {
+                    "description": "The name of the compute node which "
+                                   "need maintenance",
+                    "type": "string",
+                },
+                "backup_node": {
+                    "description": "The name of the compute node which "
+                                   "will backup the maintenance node.",
+                    "type": "string",
+                },
+            },
+            "required": ["maintenance_node"],
+        }
+
+    def get_disabled_compute_nodes_with_reason(self, reason=None):
+        return {uuid: cn for uuid, cn in
+                self.compute_model.get_all_compute_nodes().items()
+                if cn.state == element.ServiceState.ONLINE.value and
+                cn.status == element.ServiceState.DISABLED.value and
+                cn.disabled_reason == reason}
+
+    def get_disabled_compute_nodes(self):
+        return self.get_disabled_compute_nodes_with_reason(
+            self.REASON_FOR_DISABLE)
+
+    def get_instance_state_str(self, instance):
+        """Get instance state in string format"""
+        if isinstance(instance.state, six.string_types):
+            return instance.state
+        elif isinstance(instance.state, element.InstanceState):
+            return instance.state.value
+        else:
+            LOG.error('Unexpected instance state type, '
+                      'state=%(state)s, state_type=%(st)s.',
+                      dict(state=instance.state,
+                           st=type(instance.state)))
+            raise wexc.WatcherException
+
+    def get_node_status_str(self, node):
+        """Get node status in string format"""
+        if isinstance(node.status, six.string_types):
+            return node.status
+        elif isinstance(node.status, element.ServiceState):
+            return node.status.value
+        else:
+            LOG.error('Unexpected node status type, '
+                      'status=%(status)s, status_type=%(st)s.',
+                      dict(status=node.status,
+                           st=type(node.status)))
+            raise wexc.WatcherException
+
+    def get_node_capacity(self, node):
+        """Collect cpu, ram and disk capacity of a node.
+
+        :param node: node object
+        :return: dict(cpu(cores), ram(MB), disk(B))
+        """
+        return dict(cpu=node.vcpus,
+                    ram=node.memory,
+                    disk=node.disk_capacity)
+
+    def get_node_used(self, node):
+        """Collect cpu, ram and disk used of a node.
+
+        :param node: node object
+        :return: dict(cpu(cores), ram(MB), disk(B))
+        """
+        vcpus_used = 0
+        memory_used = 0
+        disk_used = 0
+        for instance in self.compute_model.get_node_instances(node):
+            vcpus_used += instance.vcpus
+            memory_used += instance.memory
+            disk_used += instance.disk
+
+        return dict(cpu=vcpus_used,
+                    ram=memory_used,
+                    disk=disk_used)
+
+    def get_node_free(self, node):
+        """Collect cpu, ram and disk free of a node.
+
+        :param node: node object
+        :return: dict(cpu(cores), ram(MB), disk(B))
+        """
+        node_capacity = self.get_node_capacity(node)
+        node_used = self.get_node_used(node)
+        return dict(cpu=node_capacity['cpu']-node_used['cpu'],
+                    ram=node_capacity['ram']-node_used['ram'],
+                    disk=node_capacity['disk']-node_used['disk'],
+                    )
+
+    def host_fits(self, source_node, destination_node):
+        """check host fits
+
+        return True if VMs could intensively migrate
+        from source_node to destination_node.
+        """
+
+        source_node_used = self.get_node_used(source_node)
+        destination_node_free = self.get_node_free(destination_node)
+        metrics = ['cpu', 'ram']
+        for m in metrics:
+            if source_node_used[m] > destination_node_free[m]:
+                return False
+        return True
+
+    def add_action_enable_compute_node(self, node):
+        """Add an action for node enabler into the solution."""
+        params = {'state': element.ServiceState.ENABLED.value}
+        self.solution.add_action(
+            action_type=self.CHANGE_NOVA_SERVICE_STATE,
+            resource_id=node.uuid,
+            input_parameters=params)
+
+    def add_action_maintain_compute_node(self, node):
+        """Add an action for node maintenance into the solution."""
+        params = {'state': element.ServiceState.DISABLED.value,
+                  'disabled_reason': self.REASON_FOR_MAINTAINING}
+        self.solution.add_action(
+            action_type=self.CHANGE_NOVA_SERVICE_STATE,
+            resource_id=node.uuid,
+            input_parameters=params)
+
+    def enable_compute_node_if_disabled(self, node):
+        node_status_str = self.get_node_status_str(node)
+        if node_status_str != element.ServiceState.ENABLED.value:
+            self.add_action_enable_compute_node(node)
+
+    def instance_migration(self, instance, src_node, des_node=None):
+        """Add an action for instance migration into the solution.
+
+        :param instance: instance object
+        :param src_node: node object
+        :param des_node: node object. if None, the instance will be
+            migrated relying on nova-scheduler
+        :return: None
+        """
+        instance_state_str = self.get_instance_state_str(instance)
+        if instance_state_str == element.InstanceState.ACTIVE.value:
+            migration_type = 'live'
+        else:
+            migration_type = 'cold'
+
+        params = {'migration_type': migration_type,
+                  'source_node': src_node.uuid}
+        if des_node:
+            params['destination_node'] = des_node.uuid
+        self.solution.add_action(action_type=self.INSTANCE_MIGRATION,
+                                 resource_id=instance.uuid,
+                                 input_parameters=params)
+
+    def host_migration(self, source_node, destination_node):
+        """host migration
+
+        Migrate all instances from source_node to destination_node.
+        Active instances use "live-migrate",
+        and other instances use "cold-migrate"
+        """
+        instances = self.compute_model.get_node_instances(source_node)
+        for instance in instances:
+            self.instance_migration(instance, source_node, destination_node)
+
+    def safe_maintain(self, maintenance_node, backup_node=None):
+        """safe maintain one compute node
+
+        Migrate all instances of the maintenance_node intensively to the
+        backup host. If users didn't give the backup host, it will select
+        one unused node to backup the maintaining node.
+
+        It calculate the resource both of the backup node and maintaining
+        node to evaluate the migrations from maintaining node to backup node.
+        If all instances of the maintaining node can migrated to
+        the backup node, it will set the maintaining node in
+        'watcher_maintaining' status., and add the migrations to solution.
+        """
+        # If user gives a backup node with required capacity, then migrate
+        # all instances from the maintaining node to the backup node.
+        if backup_node:
+            if self.host_fits(maintenance_node, backup_node):
+                self.enable_compute_node_if_disabled(backup_node)
+                self.add_action_maintain_compute_node(maintenance_node)
+                self.host_migration(maintenance_node, backup_node)
+                return True
+
+        # If uses didn't give the backup host, select one unused node
+        # with required capacity, then migrate all instances
+        # from maintaining node to it.
+        nodes = sorted(
+            self.get_disabled_compute_nodes().values(),
+            key=lambda x: self.get_node_capacity(x)['cpu'])
+        if maintenance_node in nodes:
+            nodes.remove(maintenance_node)
+
+        for node in nodes:
+            if self.host_fits(maintenance_node, node):
+                self.enable_compute_node_if_disabled(node)
+                self.add_action_maintain_compute_node(maintenance_node)
+                self.host_migration(maintenance_node, node)
+                return True
+
+        return False
+
+    def try_maintain(self, maintenance_node):
+        """try to maintain one compute node
+
+        It firstly set the maintenance_node in 'watcher_maintaining' status.
+        Then try to migrate all instances of the maintenance node, rely
+        on nova-scheduler.
+        """
+        self.add_action_maintain_compute_node(maintenance_node)
+        instances = self.compute_model.get_node_instances(maintenance_node)
+        for instance in instances:
+            self.instance_migration(instance, maintenance_node)
+
+    def pre_execute(self):
+        LOG.debug(self.compute_model.to_string())
+
+        if not self.compute_model:
+            raise wexc.ClusterStateNotDefined()
+
+        if self.compute_model.stale:
+            raise wexc.ClusterStateStale()
+
+    def do_execute(self):
+        LOG.info(_('Executing Host Maintenance Migration Strategy'))
+
+        maintenance_node = self.input_parameters.get('maintenance_node')
+        backup_node = self.input_parameters.get('backup_node')
+
+        # if no VMs in the maintenance_node, just maintain the compute node
+        src_node = self.compute_model.get_node_by_uuid(maintenance_node)
+        if len(self.compute_model.get_node_instances(src_node)) == 0:
+            if (src_node.disabled_reason !=
+                    self.REASON_FOR_MAINTAINING):
+                self.add_action_maintain_compute_node(src_node)
+                return
+
+        if backup_node:
+            des_node = self.compute_model.get_node_by_uuid(backup_node)
+        else:
+            des_node = None
+
+        if not self.safe_maintain(src_node, des_node):
+            self.try_maintain(src_node)
+
+    def post_execute(self):
+        """Post-execution phase
+
+        This can be used to compute the global efficacy
+        """
+        LOG.debug(self.solution.actions)
+        LOG.debug(self.compute_model.to_string())
diff --git a/watcher/tests/decision_engine/strategy/strategies/test_host_maintenance.py b/watcher/tests/decision_engine/strategy/strategies/test_host_maintenance.py
new file mode 100755
index 000000000..d1c21e354
--- /dev/null
+++ b/watcher/tests/decision_engine/strategy/strategies/test_host_maintenance.py
@@ -0,0 +1,206 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2017 chinac.com
+#
+# Authors: suzhengwei<suzhengwei@chinac.com>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import mock
+
+from watcher.common import exception
+from watcher.decision_engine.model import model_root
+from watcher.decision_engine.strategy import strategies
+from watcher.tests import base
+from watcher.tests.decision_engine.model import faker_cluster_state
+
+
+class TestHostMaintenance(base.TestCase):
+
+    def setUp(self):
+        super(TestHostMaintenance, self).setUp()
+
+        # fake cluster
+        self.fake_cluster = faker_cluster_state.FakerModelCollector()
+
+        p_model = mock.patch.object(
+            strategies.HostMaintenance, "compute_model",
+            new_callable=mock.PropertyMock)
+        self.m_model = p_model.start()
+        self.addCleanup(p_model.stop)
+
+        p_audit_scope = mock.patch.object(
+            strategies.HostMaintenance, "audit_scope",
+            new_callable=mock.PropertyMock
+        )
+        self.m_audit_scope = p_audit_scope.start()
+        self.addCleanup(p_audit_scope.stop)
+
+        self.m_audit_scope.return_value = mock.Mock()
+
+        self.m_model.return_value = model_root.ModelRoot()
+        self.strategy = strategies.HostMaintenance(config=mock.Mock())
+
+    def test_exception_stale_cdm(self):
+        self.fake_cluster.set_cluster_data_model_as_stale()
+        self.m_model.return_value = self.fake_cluster.cluster_data_model
+
+        self.assertRaises(
+            exception.ClusterStateNotDefined,
+            self.strategy.execute)
+
+    def test_get_node_capacity(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid("Node_0")
+        node_capacity = dict(cpu=40, ram=132, disk=250)
+        self.assertEqual(node_capacity,
+                         self.strategy.get_node_capacity(node_0))
+
+    def test_get_node_used(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid("Node_0")
+        node_used = dict(cpu=20, ram=4, disk=40)
+        self.assertEqual(node_used,
+                         self.strategy.get_node_used(node_0))
+
+    def test_get_node_free(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid("Node_0")
+        node_free = dict(cpu=20, ram=128, disk=210)
+        self.assertEqual(node_free,
+                         self.strategy.get_node_free(node_0))
+
+    def test_host_fits(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid("Node_0")
+        node_1 = model.get_node_by_uuid("Node_1")
+        self.assertTrue(self.strategy.host_fits(node_0, node_1))
+
+    def test_add_action_enable_compute_node(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        self.strategy.add_action_enable_compute_node(node_0)
+        expected = [{'action_type': 'change_nova_service_state',
+                     'input_parameters': {
+                         'state': 'enabled',
+                         'resource_id': 'Node_0'}}]
+        self.assertEqual(expected, self.strategy.solution.actions)
+
+    def test_add_action_maintain_compute_node(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        self.strategy.add_action_maintain_compute_node(node_0)
+        expected = [{'action_type': 'change_nova_service_state',
+                     'input_parameters': {
+                         'state': 'disabled',
+                         'disabled_reason': 'watcher_maintaining',
+                         'resource_id': 'Node_0'}}]
+        self.assertEqual(expected, self.strategy.solution.actions)
+
+    def test_instance_migration(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        node_1 = model.get_node_by_uuid('Node_1')
+        instance_0 = model.get_instance_by_uuid("INSTANCE_0")
+        self.strategy.instance_migration(instance_0, node_0, node_1)
+        self.assertEqual(1, len(self.strategy.solution.actions))
+        expected = [{'action_type': 'migrate',
+                     'input_parameters': {'destination_node': node_1.uuid,
+                                          'source_node': node_0.uuid,
+                                          'migration_type': 'live',
+                                          'resource_id': instance_0.uuid}}]
+        self.assertEqual(expected, self.strategy.solution.actions)
+
+    def test_instance_migration_without_dest_node(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        instance_0 = model.get_instance_by_uuid("INSTANCE_0")
+        self.strategy.instance_migration(instance_0, node_0)
+        self.assertEqual(1, len(self.strategy.solution.actions))
+        expected = [{'action_type': 'migrate',
+                     'input_parameters': {'source_node': node_0.uuid,
+                                          'migration_type': 'live',
+                                          'resource_id': instance_0.uuid}}]
+        self.assertEqual(expected, self.strategy.solution.actions)
+
+    def test_host_migration(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        node_1 = model.get_node_by_uuid('Node_1')
+        instance_0 = model.get_instance_by_uuid("INSTANCE_0")
+        instance_1 = model.get_instance_by_uuid("INSTANCE_1")
+        self.strategy.host_migration(node_0, node_1)
+        self.assertEqual(2, len(self.strategy.solution.actions))
+        expected = [{'action_type': 'migrate',
+                     'input_parameters': {'destination_node': node_1.uuid,
+                                          'source_node': node_0.uuid,
+                                          'migration_type': 'live',
+                                          'resource_id': instance_0.uuid}},
+                    {'action_type': 'migrate',
+                     'input_parameters': {'destination_node': node_1.uuid,
+                                          'source_node': node_0.uuid,
+                                          'migration_type': 'live',
+                                          'resource_id': instance_1.uuid}}]
+        self.assertIn(expected[0], self.strategy.solution.actions)
+        self.assertIn(expected[1], self.strategy.solution.actions)
+
+    def test_safe_maintain(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_0 = model.get_node_by_uuid('Node_0')
+        node_1 = model.get_node_by_uuid('Node_1')
+        self.assertFalse(self.strategy.safe_maintain(node_0))
+        self.assertFalse(self.strategy.safe_maintain(node_1))
+
+    def test_try_maintain(self):
+        model = self.fake_cluster.generate_scenario_1()
+        self.m_model.return_value = model
+        node_1 = model.get_node_by_uuid('Node_1')
+        self.strategy.try_maintain(node_1)
+        self.assertEqual(2, len(self.strategy.solution.actions))
+
+    def test_strategy(self):
+        model = self.fake_cluster. \
+            generate_scenario_9_with_3_active_plus_1_disabled_nodes()
+        self.m_model.return_value = model
+        node_2 = model.get_node_by_uuid('Node_2')
+        node_3 = model.get_node_by_uuid('Node_3')
+        instance_4 = model.get_instance_by_uuid("INSTANCE_4")
+        if not self.strategy.safe_maintain(node_2, node_3):
+            self.strategy.try_maintain(node_2)
+        expected = [{'action_type': 'change_nova_service_state',
+                     'input_parameters': {
+                         'resource_id': 'Node_3',
+                         'state': 'enabled'}},
+                    {'action_type': 'change_nova_service_state',
+                     'input_parameters': {
+                         'resource_id': 'Node_2',
+                         'state': 'disabled',
+                         'disabled_reason': 'watcher_maintaining'}},
+                    {'action_type': 'migrate',
+                     'input_parameters': {
+                         'destination_node': node_3.uuid,
+                         'source_node': node_2.uuid,
+                         'migration_type': 'live',
+                         'resource_id': instance_4.uuid}}]
+        self.assertEqual(expected, self.strategy.solution.actions)