change two_step rebalancing such that OSD capacities are respected

xtreemfs_client/dataDistribution.py

@@ -47,6 +47,15 @@ class DataDistribution(object):
                 new_osd = osd.OSD(osd_uuid)
                 self.OSDs[osd_uuid] = new_osd
 
+    def replace_osd(self, new_osd):
+        """
+        replaces the osd with uuid new_osd.uuid by new_osd
+        :param new_osd:
+        :return:
+        """
+        assert new_osd.uuid in self.OSDs.keys()
+        self.OSDs[new_osd.uuid] = new_osd
+
     def set_osd_capacities(self, osd_capacities):
         """
         set osd capacities
@@ -410,7 +419,10 @@ class DataDistribution(object):
                     origin_osd = self.get_containing_osd(virtual_folder).uuid
                     target_osd = current_osd.uuid
                     movements[virtual_folder] = (origin_osd, target_osd)
-                    self.assign_new_osd(virtual_folder, target_osd)
+
+        for current_osd, virtual_osd in current_to_virtual_osd_matching:
+            virtual_osd.uuid = current_osd.uuid
+            self.replace_osd(virtual_osd)
 
         return movements