diff -rN -u old-config-parse/docs/configuration.rst new-config-parse/docs/configuration.rst
--- old-config-parse/docs/configuration.rst	2011-09-21 15:10:25.669487229 -0600
+++ new-config-parse/docs/configuration.rst	2011-09-21 15:10:25.929486420 -0600
@@ -417,14 +417,20 @@
 
 ``backend = disk``
 
-    The default is to store shares on the local filesystem (in
+    The storage server stores shares on the local filesystem (in
     BASEDIR/storage/shares/). For configuration details (including how to
     reserve a minimum amount of free space), see `<backends/disk.rst>`_.
 
-``backend = S3``
+``backend = s3``
 
-    The storage server can store all shares to an Amazon Simple Storage
-    Service (S3) bucket. For configuration details, see `<backends/S3.rst>`_.
+    The storage server stores all shares to an Amazon Simple Storage Service
+    (S3) bucket. For configuration details, see `<backends/S3.rst>`_.
+
+``backend = debug_discard``
+
+    The storage server stores all shares in /dev/null. This is actually used,
+    for testing. It is not recommended for storage of data that you might
+    want to retrieve in the future.
 
 
 Running A Helper
diff -rN -u old-config-parse/src/allmydata/client.py new-config-parse/src/allmydata/client.py
--- old-config-parse/src/allmydata/client.py	2011-09-21 15:10:25.756487132 -0600
+++ new-config-parse/src/allmydata/client.py	2011-09-21 15:10:25.945486664 -0600
@@ -205,24 +205,49 @@
         self._secret_holder = SecretHolder(lease_secret, self.convergence)
 
     def init_storage(self):
-        # should we run a storage server (and publish it for others to use)?
+        # Should we run a storage server (and publish it for others to use)?
         if not self.get_config("storage", "enabled", True, boolean=True):
             return
         readonly = self.get_config("storage", "readonly", False, boolean=True)
 
-        storedir = FilePath(self.basedir).child(self.STOREDIR)
+        # What sort of backend?
+        backendtype = self.get_config("storage", "backend", "disk"):
 
-        data = self.get_config("storage", "reserved_space", None)
-        reserved = None
-        try:
-            reserved = parse_abbreviated_size(data)
-        except ValueError:
-            log.msg("[storage]reserved_space= contains unparseable value %s"
-                    % data)
-        if reserved is None:
-            reserved = 0
-        discard = self.get_config("storage", "debug_discard", False,
-                                  boolean=True)
+        def config_disk_backend():
+            storedir = FilePath(self.basedir).child(self.STOREDIR)
+
+            data = self.get_config("storage", "reserved_space", None)
+            reserved = None
+            try:
+                reserved = parse_abbreviated_size(data)
+            except ValueError:
+                raise InvalidValueError("[storage]reserved_space= contains unparseable value %s"
+                                        % data)
+
+            return DiskBackend(storedir, readonly, reserved)
+
+        def config_s3_backend():
+            k
+
+
+            backend = S3Backend(xxx )
+
+        def config_null_backend():
+            return NullBackend()
+
+        backend_configgers = {
+            'disk': config_disk_backend,
+            's3': config_s3_backend,
+            'debug_discard': config_null_backend,
+            }
+
+        if backendtype not in backend_configgers:
+            raise InvalidValueError("[storage]backend= is required to be one of %s, but was \"%s\"" % (backend_configgers.keys(), quote_output(backendtype),))
+            
+
+        if backendtype == "disk":
+        elif backendtype == "s3":
+        elif backendtype == "debug_discard":
 
         expire = self.get_config("storage", "expire.enabled", False, boolean=True)
         if expire:
diff -rN -u old-config-parse/src/allmydata/node.py new-config-parse/src/allmydata/node.py
--- old-config-parse/src/allmydata/node.py	2011-09-21 15:10:25.789736662 -0600
+++ new-config-parse/src/allmydata/node.py	2011-09-21 15:10:25.947486905 -0600
@@ -40,6 +40,9 @@
 class _None: # used as a marker in get_config()
     pass
 
+class InvalidValueError(Exception):
+    """ The configured value was not valid. """
+
 class MissingConfigEntry(Exception):
     """ A required config entry was not found. """
 
diff -rN -u old-config-parse/src/allmydata/storage/backends/disk/disk_backend.py new-config-parse/src/allmydata/storage/backends/disk/disk_backend.py
--- old-config-parse/src/allmydata/storage/backends/disk/disk_backend.py	2011-09-21 15:10:25.802736466 -0600
+++ new-config-parse/src/allmydata/storage/backends/disk/disk_backend.py	2011-09-21 15:10:25.954486466 -0600
@@ -48,7 +48,7 @@
 class DiskBackend(Backend):
     implements(IStorageBackend)
 
-    def __init__(self, storedir, readonly=False, reserved_space=0, discard_storage=False):
+    def __init__(self, storedir, readonly=False, reserved_space=0):
         Backend.__init__(self)
         self._setup_storage(storedir, readonly, reserved_space, discard_storage)
         self._setup_corruption_advisory()
diff -rN -u old-config-parse/src/allmydata/test/test_backends.py new-config-parse/src/allmydata/test/test_backends.py
--- old-config-parse/src/allmydata/test/test_backends.py	2011-09-21 15:10:25.813736428 -0600
+++ new-config-parse/src/allmydata/test/test_backends.py	2011-09-21 15:10:25.955486266 -0600
@@ -374,3 +374,8 @@
         self.failUnlessReallyEqual(b.remote_read(0, datalen+20), client_data)
         # If you start reading past the end of the file you get the empty string.
         self.failUnlessReallyEqual(b.remote_read(datalen+1, 3), '')
+
+
+class TestConfigureBackends(ReallyEqualMixin):
+    def test_configure_disk_backend(self):
+        xyz
diff -rN -u old-config-parse/src/allmydata/uri.py new-config-parse/src/allmydata/uri.py
--- old-config-parse/src/allmydata/uri.py	2011-09-21 15:10:25.857736680 -0600
+++ new-config-parse/src/allmydata/uri.py	2011-09-21 15:10:25.948486665 -0600
@@ -1078,4 +1078,3 @@
         if 'hash' in k:
             unpacked[k] = base32.b2a(unpacked[k])
     return unpacked
-