adding a replica to the existing 3-server shard setup?

I have 3 mongo servers with sharded database on them.

I would like to "convert" it into a replicated system in the following way:

datacenter 1:

server_1 + server_2 + server_3 (all shards)


datacenter 2:

One big server which replicates all data from datacenter_1. It would be used for backup purposes only. No need for any elections etc.


Is there any documentation which would help me configure this, or did anyone create a similar setup? I'm looking at http://docs.mongodb.org/manual/tutorial/deploy-geographically-distributed-replica-set/, but it doesn't really apply here.