David Klee walks us through the concept of resource pools in VMware:
Resource pools are used to hierarchically partition available CPU and memory resources, and are available for use at the VMware host cluster layer.
To better prioritize certain VMs over others, especially in a highly concurrent VM farm, I recommend leveraging three resource pools for SQL Server-on-VMware environments. Tier-1 can be created with a high value of resources assigned for CPU and memory; Tier-2 is normal; Tier-3 is low. Do not manually specify the amount of shares for each, as this metric will become skewed if compute hardware is added or removed from the host cluster.
Read on to understand why and how, as well as a few more tips around resource pools.