diff --git a/cinder/backup/manager.py b/cinder/backup/manager.py
index b7acf3960fe..f6791ef7d30 100644
--- a/cinder/backup/manager.py
+++ b/cinder/backup/manager.py
@@ -71,6 +71,12 @@ backup_manager_opts = [
                      'backup service startup. If false, the backup service '
                      'will remain down until all pending backups are '
                      'deleted.',),
+    cfg.IntOpt('backup_native_threads_pool_size',
+               default=60,
+               min=20,
+               help='Size of the native threads pool for the backups.  '
+                    'Most backup drivers rely heavily on this, it can be '
+                    'decreased for specific drivers that don\'t.'),
 ]
 
 # This map doesn't need to be extended in the future since it's only
@@ -104,6 +110,7 @@ class BackupManager(manager.ThreadPoolManager):
         self.volume_rpcapi = volume_rpcapi.VolumeAPI()
         super(BackupManager, self).__init__(*args, **kwargs)
         self.is_initialized = False
+        self._set_tpool_size(CONF.backup_native_threads_pool_size)
 
     @property
     def driver_name(self):
diff --git a/cinder/manager.py b/cinder/manager.py
index ec673e77922..e478c0b438b 100644
--- a/cinder/manager.py
+++ b/cinder/manager.py
@@ -68,6 +68,7 @@ from cinder.scheduler import rpcapi as scheduler_rpcapi
 from cinder import utils
 
 from eventlet import greenpool
+from eventlet import tpool
 
 
 CONF = cfg.CONF
@@ -94,6 +95,11 @@ class Manager(base.Base, PeriodicTasks):
         self.availability_zone = CONF.storage_availability_zone
         super(Manager, self).__init__(db_driver)
 
+    def _set_tpool_size(self, nthreads):
+        # NOTE(geguileo): Until PR #472 is merged we have to be very careful
+        # not to call "tpool.execute" before calling this method.
+        tpool.set_num_threads(nthreads)
+
     @property
     def service_topic_queue(self):
         return self.cluster or self.host
diff --git a/cinder/test.py b/cinder/test.py
index 18f82ef7c0a..c8c9e6ccd3b 100644
--- a/cinder/test.py
+++ b/cinder/test.py
@@ -26,6 +26,7 @@ import os
 import sys
 import uuid
 
+from eventlet import tpool
 import fixtures
 import mock
 from oslo_concurrency import lockutils
@@ -296,6 +297,11 @@ class TestCase(testtools.TestCase):
             # added.
             self.assertRaisesRegexp = self.assertRaisesRegex
 
+        # Ensure we have the default tpool size value and we don't carry
+        # threads from other test runs.
+        tpool.killall()
+        tpool._nthreads = 20
+
     def _restore_obj_registry(self):
         objects_base.CinderObjectRegistry._registry._obj_classes = \
             self._base_test_obj_backup
diff --git a/cinder/tests/unit/backup/test_backup.py b/cinder/tests/unit/backup/test_backup.py
index 24582163666..38ea0482469 100644
--- a/cinder/tests/unit/backup/test_backup.py
+++ b/cinder/tests/unit/backup/test_backup.py
@@ -19,6 +19,7 @@ import ddt
 import os
 import uuid
 
+from eventlet import tpool
 import mock
 from os_brick.initiator.connectors import fake as fake_connectors
 from oslo_config import cfg
@@ -1641,6 +1642,27 @@ class BackupTestCase(BaseBackupTest):
         backup = self._create_backup_db_entry(volume_id=vol_id)
         self.assertFalse(backup.has_dependent_backups)
 
+    def test_default_tpool_size(self):
+        """Test we can set custom tpool size."""
+        tpool._nthreads = 20
+        self.assertListEqual([], tpool._threads)
+
+        self.backup_mgr = importutils.import_object(CONF.backup_manager)
+
+        self.assertEqual(60, tpool._nthreads)
+        self.assertListEqual([], tpool._threads)
+
+    def test_tpool_size(self):
+        """Test we can set custom tpool size."""
+        self.assertNotEqual(100, tpool._nthreads)
+        self.assertListEqual([], tpool._threads)
+
+        self.override_config('backup_native_threads_pool_size', 100)
+        self.backup_mgr = importutils.import_object(CONF.backup_manager)
+
+        self.assertEqual(100, tpool._nthreads)
+        self.assertListEqual([], tpool._threads)
+
 
 class BackupTestCaseWithVerify(BaseBackupTest):
     """Test Case for backups."""
diff --git a/cinder/tests/unit/volume/test_volume.py b/cinder/tests/unit/volume/test_volume.py
index 0c02b5ab196..855981cfcb9 100644
--- a/cinder/tests/unit/volume/test_volume.py
+++ b/cinder/tests/unit/volume/test_volume.py
@@ -2987,6 +2987,29 @@ class VolumeTestCase(base.BaseVolumeTestCase):
         self.assertRaises(exception.ProgrammingError,
                           manager._append_volume_stats, {'pools': 'bad_data'})
 
+    def test_default_tpool_size(self):
+        """Test we can set custom tpool size."""
+        eventlet.tpool._nthreads = 10
+        self.assertListEqual([], eventlet.tpool._threads)
+
+        vol_manager.VolumeManager()
+
+        self.assertEqual(20, eventlet.tpool._nthreads)
+        self.assertListEqual([], eventlet.tpool._threads)
+
+    def test_tpool_size(self):
+        """Test we can set custom tpool size."""
+        self.assertNotEqual(100, eventlet.tpool._nthreads)
+        self.assertListEqual([], eventlet.tpool._threads)
+
+        self.override_config('backend_native_threads_pool_size', 100,
+                             group='backend_defaults')
+        vol_manager.VolumeManager()
+
+        self.assertEqual(100, eventlet.tpool._nthreads)
+        self.assertListEqual([], eventlet.tpool._threads)
+        eventlet.tpool._nthreads = 20
+
 
 class VolumeTestCaseLocks(base.BaseVolumeTestCase):
     MOCK_TOOZ = False
diff --git a/cinder/volume/manager.py b/cinder/volume/manager.py
index 4635f1a5d0e..da95bf5243a 100644
--- a/cinder/volume/manager.py
+++ b/cinder/volume/manager.py
@@ -143,6 +143,12 @@ volume_backend_opts = [
     cfg.BoolOpt('suppress_requests_ssl_warnings',
                 default=False,
                 help='Suppress requests library SSL certificate warnings.'),
+    cfg.IntOpt('backend_native_threads_pool_size',
+               default=20,
+               min=20,
+               help='Size of the native threads pool for the backend.  '
+                    'Increase for backends that heavily rely on this, like '
+                    'the RBD driver.'),
 ]
 
 CONF = cfg.CONF
@@ -190,6 +196,8 @@ class VolumeManager(manager.CleanableManager,
         service_name = service_name or 'backend_defaults'
         self.configuration = config.Configuration(volume_backend_opts,
                                                   config_group=service_name)
+        self._set_tpool_size(
+            self.configuration.backend_native_threads_pool_size)
         self.stats = {}
         self.service_uuid = None
 
diff --git a/releasenotes/notes/tpool-size-11121f78df24db39.yaml b/releasenotes/notes/tpool-size-11121f78df24db39.yaml
new file mode 100644
index 00000000000..de06f2400f4
--- /dev/null
+++ b/releasenotes/notes/tpool-size-11121f78df24db39.yaml
@@ -0,0 +1,15 @@
+---
+features:
+  - Adds support to configure the size of the native thread pool used by the
+    cinder volume and backup services.  For the backup we use
+    `backup_native_threads_pool_size` in the `[DEFAULT]` section, and for the
+    backends we use `backend_native_threads_pool_size` in the driver section.
+
+fixes:
+  - Fixes concurrency issue on backups, where only 20 native threads could be
+    concurrently be executed.  Now default will be 60, and can be changed with
+    `backup_native_threads_pool_size`.
+  - RBD driver can have bottlenecks if too many slow operations are happening
+    at the same time (for example many huge volume deletions), we can now use
+    the `backend_native_threads_pool_size` option in the RBD driver section to
+    resolve the issue.