Many CPU and memory resources were calculated in the earlier recipes in this chapter, and are as follows:

• The total number of CPU resources required is 167 GHz
• The total number of memory resources required, taking into account a 25% savings for transparent page sharing, is 657 GB

Based on the design factors, the determination can be made on whether a host should be designed to scale up or scale out. In this case, the following design information provides what is needed to size the individual host resources:

• Currently, there are 100 physical servers, each hosting a single application. Each application services 10 customers
• No more than 20 application servers (or 200 customers) should be affected by a hardware failure
• The business expects to add 50 new customers over the next year
• Support growth over the next five years

Based on the requirements, the total number of hosts that are required to support the current workloads, the future workloads, and the redundancy requirements can be calculated as follows:

Use the following equation to determine the number of CPU resources that are required per host (the failover hosts are not included here because these resources are effectively reserved for failover):

Use the following equation to determine the number of memory resources that are required per host (as with CPU resources, the failover hosts are not included in the calculation):

Each physical host will need to be sized to support 20 virtual machines, and will require 23.8 GHz of CPU resources and 94 GB of memory resources.