title: Sharded mongodb won't redistribute data
body: <p>I've setup a sharded mongo db environment on localhost, with 3 config servers and 2 sharded mongo instances and a single mongos.</p>
  
  <p>Once the cluster has started up, I run the following sequence of commands:</p>
  
  <pre><code>sh.addShard( "127.0.0.1:27010")
  sh.addShard( "127.0.0.1:27011")
  
  a = {"_id" : 1, "value" : 1}
  b = {"_id" : 2, "value" : 2}
  c = {"_id" : 3, "value" : 3}
  d = {"_id" : 4, "value" : 4}
  
  use foobar;
  db.foo.insert(a);
  db.foo.insert(b);
  db.foo.insert(c);
  db.foo.insert(d);
  </code></pre>
  
  <p>The I enable the db for sharding and create an index etc.</p>
  
  <pre><code>sh.enableSharding("foobar");
  db.foo.ensureIndex({"value":"hashed"});
  sh.shardCollection("foobar.foo", { value: "hashed" } )
  </code></pre>
  
  <p>The result of all the above operations is successful.</p>
  
  <p>But once I do:
      db.foo.stats()</p>
  
  <p>I see that all the data ends just in one shard without being distributed. And running</p>
  
  <pre><code>db.printShardingStatus();
  </code></pre>
  
  <p>produces: </p>
  
  <pre><code>--- Sharding Status --- 
  sharding version: {
  "_id" : 1,
  "version" : 3,
  "minCompatibleVersion" : 3,
  "currentVersion" : 4,
  "clusterId" : ObjectId("52170e8a7633066f09e0c9d3")
  }
   shards:
  {  "_id" : "shard0000",  "host" : "127.0.0.1:27010" }
  {  "_id" : "shard0001",  "host" : "127.0.0.1:27011" }
   databases:
  {  "_id" : "admin",  "partitioned" : false,  "primary" : "config" }
  {  "_id" : "foobar",  "partitioned" : true,  "primary" : "shard0000" }
      foobar.foo
          shard key: { "value" : "hashed" }
          chunks:
              shard0000   1
          { "value" : { "$minKey" : 1 } } --&gt;&gt; { "value" : { "$maxKey" : 1 } } on : shard0000 Timestamp(1, 0) 
  </code></pre>
  
  <p>Interestingly, though, if I start off with a blank collection and have enable sharding on it before adding any data to it, the results are very different:</p>
  
  <pre><code>db.foo.stats();
  {
  "sharded" : true,
  "ns" : "foobar.foo",
  "count" : 4,
  "numExtents" : 2,
  "size" : 144,
  "storageSize" : 16384,
  "totalIndexSize" : 32704,
  "indexSizes" : {
      "_id_" : 16352,
      "value_hashed" : 16352
  },
  "avgObjSize" : 36,
  "nindexes" : 2,
  "nchunks" : 4,
  "shards" : {
      "shard0000" : {
          "ns" : "foobar.foo",
          "count" : 1,
          "size" : 36,
          "avgObjSize" : 36,
          "storageSize" : 8192,
          "numExtents" : 1,
          "nindexes" : 2,
          "lastExtentSize" : 8192,
          "paddingFactor" : 1,
          "systemFlags" : 1,
          "userFlags" : 0,
          "totalIndexSize" : 16352,
          "indexSizes" : {
              "_id_" : 8176,
              "value_hashed" : 8176
          },
          "ok" : 1
      },
      "shard0001" : {
          "ns" : "foobar.foo",
          "count" : 3,
          "size" : 108,
          "avgObjSize" : 36,
          "storageSize" : 8192,
          "numExtents" : 1,
          "nindexes" : 2,
          "lastExtentSize" : 8192,
          "paddingFactor" : 1,
          "systemFlags" : 1,
          "userFlags" : 0,
          "totalIndexSize" : 16352,
          "indexSizes" : {
              "_id_" : 8176,
              "value_hashed" : 8176
          },
          "ok" : 1
      }
  },
  "ok" : 1
  }
  </code></pre>
  
  <p>So the question is whether I'm missing something, if I shard an existing collection?</p>