diff --git a/nova/cells/state.py b/nova/cells/state.py
index a53ae50cafea..e83396cf5686 100644
--- a/nova/cells/state.py
+++ b/nova/cells/state.py
@@ -16,6 +16,7 @@
 """
 CellState Manager
 """
+import collections
 import copy
 import datetime
 import functools
@@ -259,7 +260,10 @@ class CellStateManager(base.Base):
             ctxt = context.get_admin_context()
 
         reserve_level = CONF.cells.reserve_percent / 100.0
-        compute_hosts = {}
+
+        def _defaultdict_int():
+            return collections.defaultdict(int)
+        compute_hosts = collections.defaultdict(_defaultdict_int)
 
         def _get_compute_hosts():
             service_refs = {service.host: service
@@ -273,11 +277,13 @@ class CellStateManager(base.Base):
                 if not service or service['disabled']:
                     continue
 
-                compute_hosts[host] = {
-                        'free_ram_mb': compute['free_ram_mb'],
-                        'free_disk_mb': compute['free_disk_gb'] * 1024,
-                        'total_ram_mb': compute['memory_mb'],
-                        'total_disk_mb': compute['local_gb'] * 1024}
+                chost = compute_hosts[host]
+                chost['free_ram_mb'] += compute['free_ram_mb']
+                free_disk = compute['free_disk_gb'] * 1024
+                chost['free_disk_mb'] += free_disk
+                chost['total_ram_mb'] += compute['memory_mb']
+                total_disk = compute['local_gb'] * 1024
+                chost['total_disk_mb'] += total_disk
 
         _get_compute_hosts()
         if not compute_hosts:
diff --git a/nova/tests/unit/cells/test_cells_state_manager.py b/nova/tests/unit/cells/test_cells_state_manager.py
index a6179082a0d4..a35415e85928 100644
--- a/nova/tests/unit/cells/test_cells_state_manager.py
+++ b/nova/tests/unit/cells/test_cells_state_manager.py
@@ -38,6 +38,13 @@ FAKE_COMPUTES = [
     ('host4', 1024, 100, 300, 30),
 ]
 
+FAKE_COMPUTES_N_TO_ONE = [
+    ('host1', 1024, 100, 0, 0),
+    ('host1', 1024, 100, -1, -1),
+    ('host2', 1024, 100, 1024, 100),
+    ('host2', 1024, 100, 300, 30),
+]
+
 # NOTE(alaski): It's important to have multiple types that end up having the
 # same memory and disk requirements.  So two types need the same first value,
 # and two need the second and third values to add up to the same thing.
@@ -49,16 +56,12 @@ FAKE_ITYPES = [
 ]
 
 
-@classmethod
-def _fake_compute_node_get_all(cls, context):
-    def _node(host, total_mem, total_disk, free_mem, free_disk):
-        return objects.ComputeNode(host=host,
-                                   memory_mb=total_mem,
-                                   local_gb=total_disk,
-                                   free_ram_mb=free_mem,
-                                   free_disk_gb=free_disk)
-
-    return [_node(*fake) for fake in FAKE_COMPUTES]
+def _create_fake_node(host, total_mem, total_disk, free_mem, free_disk):
+    return objects.ComputeNode(host=host,
+                               memory_mb=total_mem,
+                               local_gb=total_disk,
+                               free_ram_mb=free_mem,
+                               free_disk_gb=free_disk)
 
 
 @classmethod
@@ -69,6 +72,16 @@ def _fake_service_get_all_by_binary(cls, context, binary):
     return [_node(*fake) for fake in FAKE_COMPUTES]
 
 
+@classmethod
+def _fake_compute_node_get_all(cls, context):
+    return [_create_fake_node(*fake) for fake in FAKE_COMPUTES]
+
+
+@classmethod
+def _fake_compute_node_n_to_one_get_all(cls, context):
+    return [_create_fake_node(*fake) for fake in FAKE_COMPUTES_N_TO_ONE]
+
+
 def _fake_cell_get_all(context):
     return []
 
@@ -187,6 +200,35 @@ class TestCellsStateManager(test.NoDBTestCase):
         return my_state.capacities
 
 
+class TestCellsStateManagerNToOne(TestCellsStateManager):
+    def setUp(self):
+        super(TestCellsStateManagerNToOne, self).setUp()
+
+        self.stubs.Set(objects.ComputeNodeList, 'get_all',
+                       _fake_compute_node_n_to_one_get_all)
+
+    def test_capacity_part_reserve(self):
+        # utilize half the cell's free capacity
+        cap = self._capacity(50.0)
+
+        cell_free_ram = sum(compute[3] for compute in FAKE_COMPUTES_N_TO_ONE)
+        self.assertEqual(cell_free_ram, cap['ram_free']['total_mb'])
+
+        cell_free_disk = (1024 *
+                sum(compute[4] for compute in FAKE_COMPUTES_N_TO_ONE))
+        self.assertEqual(cell_free_disk, cap['disk_free']['total_mb'])
+
+        self.assertEqual(0, cap['ram_free']['units_by_mb']['0'])
+        self.assertEqual(0, cap['disk_free']['units_by_mb']['0'])
+
+        units = 6  # 6 from host 2
+        self.assertEqual(units, cap['ram_free']['units_by_mb']['50'])
+
+        sz = 25 * 1024
+        units = 1  # 1 on host 2
+        self.assertEqual(units, cap['disk_free']['units_by_mb'][str(sz)])
+
+
 class TestCellStateManagerException(test.NoDBTestCase):
     @mock.patch.object(time, 'sleep')
     def test_init_db_error(self, mock_sleep):