convert sharded mongo cluster to two cluster

Hi, Buddy,

     We want to migrate the mongodb cluster from IDC1 to IDC2. The mongo version is v2.2. data size is about 10 TB with shards and replica set. 

     I read the document about backup stategieshttp://docs.mongodb.org/v2.2/administration/backups/#sharded-cluster-backups, it is difficult to dump large backup file.

     The step i considered is as following :

     1. add a secondary in IDC2 to IDC1 cluster. One secondary in IDC2 join to One Shard in IDC1.

     2. the secondary in IDC2 syncing data from IDC1.

     3. convert the secondary in IDC2 to new Cluster. Now there is two standalone cluster: one in IDC2 another in IDC1. 

     4. do other things... (ignore please)

     I am not sure about step3 is executable? And how to do? Could anybody give some idea?