$$ \text{Single Server} \to \text{Rack} \to Cluster $$ A pre-packaged compute between a server & cluster.
- Contains ~42 rack units/RU that host computing resources.
- Contains CPU, accelerators, storage (cold/warm/hot disks + SSDs) and a networking interconnect (see [[Software Defined Networking]])
The future is full resource disaggregation, the system no longer provisions applications servers with resources, but rather has pooled all the resources in the rack (or even datacentre) for applications to use as if running on a single machine.
Rack scale applications can use [[Remote Direct Memory Access]]