Resource pools hierarchically partition the available CPU and memory resources. When you configure separate resource pools, you have more options when you need to choose between resource availability and load balancing.

You may want to use resource pools to isolate performance. Isolation can prevent one VM's performance from affecting the performance of other VMs. This way, your defined limits provide more predictable service levels and less resource contention. If you define limits on your resource pool, then it also protects the resource pool from a VM going into a runaway condition. You may also want to set a firm limit on a resource pool, which reduces the negative effect that the VM might have in the resource pool.

VMware recommends that resource pools and VMs should not be made siblings in a hierarchy. Instead, each hierarchy level should contain only resource pools or VMs. By default, resource pools are assigned share values that might not compare appropriately with those assigned to VMs, potentially resulting in unexpected performance.