Question

So I was reading this documentation on changing config servers:
http://www.mongodb.org/display/DOCS/Changing+Config+Servers

While I am okay with the order of steps for this operation:
Renaming a config server – different host name
If you wish to use a different name or ip address in the –configdb option then this applies to you.

1. Shutdown config server you want to move
2. Move data to new machine
3. Start new config server
4. Shutdown all processes (mongod, mongos, config server).
5. Restart mongod processes.
6. Restart mongos processes with the new –configdb parameter.

Is there any specific reason for reversing the order of the last two steps in this:
Upgrading from one config server to three
Unfortunately you will need to shutdown the entire system.

1. Shutdown all processes (mongod, mongos, config server).
2. Copy the data subdirectories (dbpath tree) from the config server to the new config servers.
3. Start the config servers.
4. Restart mongos processes with the new –configdb parameter.
5. Restart mongod processes.

Answer 1

In general we suggest starting the mongos after the mongod and the config servers are up. We’ve made the docs consistent on this point.