Node Manager manages compute resources in a cloud environment, where the number of compute nodes can be scaled as needed.
Node Manager starts and stops compute nodes on demand, taking into account site parameters (e.g. a desired number of permanent compute nodes).
For a bare metal Arvados installation the number of compute nodes tends to be static, which means Node Manager is not needed.
Node Manager currently supports Amazon EC2 (AWS), Google Compute Engine, and Microsoft Azure.
Please see the Hacking Node Manager page.