Add warning about possible misuse of replicas

TODO

@@ -71,6 +71,8 @@ RC  - Review output of pylint (CODE)
       Some methods might not implement proper transaction isolation when they
       should. An example is object history (undoLog), which can see data
       committed by future transactions.
+    - Add a 'devid' storage configuration so that master do not distribute
+      replicated partitions on storages with same 'devid'.
 
     Storage
     - Use HailDB instead of a stand-alone MySQL server.

neo.conf

@@ -22,7 +22,10 @@ masters: 127.0.0.1:10000
 # Replicas: How many copies of a partition should exist at a time.
 #   0 means no redundancy
 #   1 means there is a spare copy of all partitions
-replicas: 1
+replicas: 0
+# IMPORTANT: NEO does not try to spread replicas on different physical devices
+#            so replicas should not be used if you have at least 2 nodes
+#            storing data on the same device.
 # Partitions: How data spreads among storage nodes.
 # IMPORTANT: This can not be changed once the cluster contains data.
 partitions: 12