diff --git a/Doc/library/os.rst b/Doc/library/os.rst
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -798,7 +798,7 @@
    Availability: Unix.
 
 
-.. function:: fsync(fd)
+.. function:: fsync(fd, full_sync=False)
 
    Force write of file with filedescriptor *fd* to disk.  On Unix, this calls the
    native :c:func:`fsync` function; on Windows, the MS :c:func:`_commit` function.
@@ -807,6 +807,15 @@
    ``f.flush()``, and then do ``os.fsync(f.fileno())``, to ensure that all internal
    buffers associated with *f* are written to disk.
 
+   The POSIX standart requires that :c:func:`fsync` must transfer the buffered
+   data to the storage device, not that the data is actually written by the
+   device itself.  It explicitely leaves it up to operating system implementors
+   whether users are given stronger guarantees on data integrity or not.  Some
+   systems also offer special functions which overtake the part of making such
+   stronger guarantees, i.e., Mac OS X and NetBSD.  The optional *full_sync*
+   argument can be used to enforce usage of these special functions if that is
+   appropriate for the *fd* in question.
+
    Availability: Unix, and Windows.
 
 
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -837,10 +837,10 @@
     singles = ["fchdir", "dup", "fdopen", "fdatasync", "fstat",
                "fstatvfs", "fsync", "tcgetpgrp", "ttyname"]
     #singles.append("close")
-    #We omit close because it doesn'r raise an exception on some platforms
+    # We omit close because it doesn't raise an exception on some platforms
     def get_single(f):
         def helper(self):
-            if  hasattr(os, f):
+            if hasattr(os, f):
                 self.check(getattr(os, f))
         return helper
     for f in singles:
@@ -855,6 +855,11 @@
             self.fail("%r didn't raise a OSError with a bad file descriptor"
                       % f)
 
+    def test_fsync_arg(self):
+        if hasattr(os, "fsync"):
+            self.check(os.fsync, True)
+            self.check(os.fsync, False)
+
     def test_isatty(self):
         if hasattr(os, "isatty"):
             self.assertEqual(os.isatty(support.make_bad_fd()), False)
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2121,13 +2121,50 @@
 
 #ifdef HAVE_FSYNC
 PyDoc_STRVAR(posix_fsync__doc__,
-"fsync(fildes)\n\n\
-force write of file with filedescriptor to disk.");
-
-static PyObject *
-posix_fsync(PyObject *self, PyObject *fdobj)
-{
-    return posix_fildes(fdobj, fsync);
+"fsync(fildes, full_sync=False)\n\n"
+"force write of file buffers with fildes to disk;\n"
+"full_sync forces flush of disk caches in case fsync() alone is not enough.");
+
+static PyObject *
+posix_fsync(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+    PyObject *fdobj;
+    int full_sync = 0;
+    static char *keywords[] = {"fd", "full_sync", NULL };
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|i", keywords,
+                                     &fdobj, &full_sync))
+        return NULL;
+
+    /* See issue 11877 discussion */
+# if ((defined __APPLE__ && defined F_FULLFSYNC) || \
+      (defined __NetBSD__ && defined FDISKSYNC))
+    if (full_sync != 0) {
+        int res, fd = PyObject_AsFileDescriptor(fdobj);
+        if (fd < 0)
+            return NULL;
+        if (!_PyVerify_fd(fd))
+            return posix_error();
+
+        Py_BEGIN_ALLOW_THREADS
+#  if defined __APPLE__
+        /* F_FULLFSYNC is not supported for all types of FDs/FSYSs;
+         * be on the safe side and test for inappropriate ioctl errors */
+        res = fcntl(fd, F_FULLFSYNC);
+        if (res < 0 && errno == ENOTTY)
+            res = fsync(fd);
+#  elif defined __NetBSD__
+        res = fsync_range(fd, FFILESYNC|FDISKSYNC, 0, 0);
+#  endif
+        Py_END_ALLOW_THREADS
+
+        if (res < 0)
+            return posix_error();
+        Py_INCREF(Py_None);
+        return Py_None;
+    } else
+# endif
+        return posix_fildes(fdobj, fsync);
 }
 #endif /* HAVE_FSYNC */
 
@@ -9472,7 +9509,8 @@
     {"fchdir",          posix_fchdir, METH_O, posix_fchdir__doc__},
 #endif
 #ifdef HAVE_FSYNC
-    {"fsync",       posix_fsync, METH_O, posix_fsync__doc__},
+    {"fsync",           (PyCFunction)posix_fsync, METH_VARARGS|METH_KEYWORDS,
+                        posix_fsync__doc__},
 #endif
 #ifdef HAVE_SYNC
     {"sync",        posix_sync, METH_NOARGS, posix_sync__doc__},