I want to distribute a sharded/replicated MongoDB setup across multiple of Amazon\'s EC2 regions. Is this traffic already encrypted by MongoDB or can I optionally set this up? O
If you're not running on EC2, these solutions aren't really an option. There is another way and that is to set up your own IaaS provider independent VPC. vCider has a solution for this that works well with Mongo as well as Cassandra. For Cassandra securing client/DB traffic is especially painful since there is no native encryption.
Good example of how this all works here:
http://www.vcider.com/vpc-deployments/secure-saas
As far as Cassandra goes, some benchmark info here.
http://blog.vcider.com/2011/09/virtual-networks-can-run-cassandra-up-to-60-faster/
With native encryption in the kernel you can run much faster.