HPC clusters and supercomputers resources are accounted in either core-hours or node-hours (and more generally CPU-hours). One core-hour is equal to one core used for one wall-clock hour computed from the time the core is allocated to the time it is deallocated.
The total resource available is computed by multiplying the total amount of nodes available for computations by the total allocation time in hours. For instance, a 400-node cluster will provide 400*24*365 = 3'504'000 node-hours over one year.
Users are typically given a percentage of the total resource, which has a node-hours equivalent. For instance, 10% of the HPC cluster means 40-node hours over 1 year = 350'400 node-hours.
use workload manager to dispatch jobs. Resources
The fair-share algorithm in SLURM is described at http://slurm.schedmd.com/fair_tree.html.