Once the total CPU and memory resource requirements have been calculated, the amount of resources per host must be determined. Host resources can be designed based on two resource-scaling methodologies: scaling up or scaling out.
When scaling up, fewer, larger hosts are used to satisfy the resource requirements. More virtual machines run on a single host; because of this, more virtual machines are also affected by a host failure.
When scaling out, many smaller hosts are used to satisfy the resource requirements. Fewer virtual machines run on a single host, and fewer virtual machines will be affected by a host failure.