Fixed Fee (in ADA).
Per the recommended setup, we have at a minimum a relay node (relay1.sabbathstake.com) like a firewall in front of the producer node. This means at least two copies of the Cardano blockchain are always maintained.
Running on Linux, the operating system that runs the Internet, a stable base is provided. On top of that is running the current Cardano node software.
For Cardano network diversity we chose to host with Linode in Dallas, Tx.