diff --git a/doc/source/development_saio.rst b/doc/source/development_saio.rst
index bca218cad5..1d497a526f 100644
--- a/doc/source/development_saio.rst
+++ b/doc/source/development_saio.rst
@@ -591,3 +591,17 @@ doesn't work, here are some good starting places to look for issues:
    you check that you can ``GET`` account, use ``sudo service memcached status``
    and check if memcache is running. If memcache is not running, start it using
    ``sudo service memcached start``. Once memcache is running, rerun ``GET`` account.
+
+------------
+Known Issues
+------------
+
+Listed here are some "gotcha's" that you may run into when using or testing your SAIO:
+
+#. fallocate_reserve - in most cases a SAIO doesn't have a very large XFS partition
+   so having fallocate enabled and fallocate_reserve set can cause issues, specifically
+   when trying to run the functional tests. For this reason fallocate has been turned
+   off on the object-servers in the SAIO. If you want to play with the fallocate_reserve
+   settings then know that functional tests will fail unless you change the max_file_size
+   constraint to something more reasonable then the default (5G). Ideally you'd make
+   it 1/4 of your XFS file system size so the tests can pass.
diff --git a/swift/common/utils.py b/swift/common/utils.py
index a33df51ed8..4694f5951e 100644
--- a/swift/common/utils.py
+++ b/swift/common/utils.py
@@ -596,7 +596,8 @@ class FileLikeIter(object):
 class FallocateWrapper(object):
 
     def __init__(self, noop=False):
-        if noop:
+        self.noop = noop
+        if self.noop:
             self.func_name = 'posix_fallocate'
             self.fallocate = noop_libc_function
             return
@@ -614,16 +615,18 @@ class FallocateWrapper(object):
 
     def __call__(self, fd, mode, offset, length):
         """The length parameter must be a ctypes.c_uint64."""
-        if FALLOCATE_RESERVE > 0:
-            st = os.fstatvfs(fd)
-            free = st.f_frsize * st.f_bavail - length.value
-            if FALLOCATE_IS_PERCENT:
-                free = (float(free) / float(st.f_frsize * st.f_blocks)) * 100
-            if float(free) <= float(FALLOCATE_RESERVE):
-                raise OSError(
-                    errno.ENOSPC,
-                    'FALLOCATE_RESERVE fail %s <= %s' % (free,
-                                                         FALLOCATE_RESERVE))
+        if not self.noop:
+            if FALLOCATE_RESERVE > 0:
+                st = os.fstatvfs(fd)
+                free = st.f_frsize * st.f_bavail - length.value
+                if FALLOCATE_IS_PERCENT:
+                    free = \
+                        (float(free) / float(st.f_frsize * st.f_blocks)) * 100
+                if float(free) <= float(FALLOCATE_RESERVE):
+                    raise OSError(
+                        errno.ENOSPC,
+                        'FALLOCATE_RESERVE fail %s <= %s' %
+                        (free, FALLOCATE_RESERVE))
         args = {
             'fallocate': (fd, mode, offset, length),
             'posix_fallocate': (fd, offset, length)
diff --git a/test/unit/common/test_utils.py b/test/unit/common/test_utils.py
index 9b9ffe9b14..14e826c908 100644
--- a/test/unit/common/test_utils.py
+++ b/test/unit/common/test_utils.py
@@ -2601,6 +2601,19 @@ cluster_dfw1 = http://dfw1.host/v1/
         try:
             fallocate = utils.FallocateWrapper(noop=True)
             utils.os.fstatvfs = fstatvfs
+
+            # Make sure setting noop, which disables fallocate, also stops the
+            # fallocate_reserve check.
+            # Set the fallocate_reserve to 99% and request an object that is
+            # about 50% the size. With fallocate_reserve off this will succeed.
+            utils.FALLOCATE_RESERVE, utils.FALLOCATE_IS_PERCENT = \
+                utils.config_fallocate_value('99%')
+            self.assertEqual(fallocate(0, 1, 0, ctypes.c_uint64(500)), 0)
+
+            # Setting noop to False after the constructor allows us to use
+            # a noop fallocate syscall and still test fallocate_reserve.
+            fallocate.noop = False
+
             # Want 1023 reserved, have 1024 * 1 free, so succeeds
             utils.FALLOCATE_RESERVE, utils.FALLOCATE_IS_PERCENT = \
                 utils.config_fallocate_value('1023')