Checksums

Restarting all nodes simultaneously in a distributed system can be a bit hard, and leads to longer downtime.
I think it will probably be easier to restart the nodes 1 by 1. At a certain point the majority switches from the old nodes to the new ones.
You probably want to keep things easy by not having old and new nodes communicate with each other, right?
This can be done by either
- changing the port of the inter node communication or
- by having some magic mismatch when a connection is made between old and new nodes (I'm not sure if there currently is a magic ... this option would probably protect better against operator errors, so therefor I would prefer it)