Why the specific requirements for the disk storage and memory?

The SKALE Network is designed to be highly performant with high throughput and low latency. On-chain storage is also an important offering of the network and so disk storage needs to be above a certain amount in order to support this capability. Nodes operate as virtualized nodes, meaning that one node can service many elastic sidechains. Sidechains sizes can be small, medium, or large with a small chain using 1/128 of a node’s resources, a medium using 1/8 of the resources, and a large using the full amount. We should also mention the future that the SKALE Network is building towards is one where decentralized solutions will make use of a number of elastic sidechains – not unlike the way cloud applications today make use of multiple microservice meshes and/or database clusters, each one optimized for the app features or capabilities it is supporting. This concept is explored further in an article on monolithic architectures vs multiple side chains here.