Upgrading Mongo From 2.7 -> 3.0

• disable balancer in mongo shell

1	sh.stopBalancer()

• upgrade 1 mongos to upgrade the cluster metadata

1	mongos --configdb configDB string --upgrade

• upgrade the rest of mongos

• upgrade the config servers starting with the last in the config string

• Upgrade each shard

• re-enable balancer in mongo shell

1	sh.startBalancer()