Explain resources

[Sabryr]

Explain the resource before " "30-batch-system.md".

1. What is a node
2. What is a core, what do you get when you ask for "ntasks" "cpu"
3. What will happen if number of nodes not specified (where in how many nodes will your job be distributed)

[ChristinaLK]

This would be in 20-architecture.

[markcmiller86]

So, if the 20- section is really to be named architecture, I wonder if it indeed does make sense to describe nodes other than login and compute there simply for completeness. Generally, an architecture description will include storage at least, as well as off-cluster connectivity such as from gateway nodes. And, knowing those aspects of the architecture can be important in making decisions regarding the use of tools (e.g. htar) to move files or the way files will be written in storage. So, I am waffling now on this issue of node types to describe.