added use cases page

docs/index.rst

@@ -28,6 +28,7 @@ Contents:
    api
    replication
    failover
+   usecases
 
 
 Indices and tables

docs/usecases.rst

@@ -0,0 +1,55 @@
+Use cases
+===================
+
+Saving image with different sizes
+#############################
+
+Each image usually store one file key in database. However, one image can have several versions, e.g., thumbnail, small, medium, large, original. And each version of the same image will have a file key. It's not ideal to store all the keys.
+
+One way to resolve this is here.
+
+Reserve a set of file keys, for example, 5
+
+.. code-block:: bash
+
+	curl http://<host>:<port>/dir/assign?count=5
+	{"fid":"3,01637037d6","url":"127.0.0.1:8080","publicUrl":"localhost:8080","count":5}
+
+Save the 5 versions of the image to the volume server. The urls for each image can be:
+
+.. code-block:: bash
+
+	http://<url>:<port>/3,01637037d6
+	http://<url>:<port>/3,01637037d6_1
+	http://<url>:<port>/3,01637037d6_2
+	http://<url>:<port>/3,01637037d6_3
+	http://<url>:<port>/3,01637037d6_4
+
+Overwriting mime types
+#############################
+
+The correct way to send mime type:
+
+
+.. code-block:: bash
+
+	curl -F "file=@myImage.png;type=image/png" http://127.0.0.1:8081/5,2730a7f18b44
+
+The wrong way to send it:
+
+.. code-block:: bash
+
+	curl -H "Content-Type:image/png" -F file=@myImage.png http://127.0.0.1:8080/5,2730a7f18b44
+	
+Securing WeedFS
+#############################
+
+The simple way is to front all master and volume servers with firewall.
+
+However, if blocking servicing port is not feasible or trivial, a white list option can be used. Only traffic from the white list IP addresses have write permission.
+
+.. code-block:: bash
+
+	weed master -whiteList="::1,127.0.0.1"
+	weed volume -whiteList="::1,127.0.0.1"
+	# "::1" is for IP v6 localhost.