vmware cloud infrastructure

Compute Resources for VMware vSphere Cloud Infrastructure

This article explains on how to estimate required number for VMware ESXi hosts to setup your own VMware vSphere cloud infrastructure.

To determine the required number of VMware ESXi hosts that is needed to consolidate virtualization candidates, performance and utilization can been analyzed using VMware Capacity Planner.

VMware ESXi Host CPU and Memory Requirements

For this exercise let’s assume as a result of CPU and Memory analysis we have got the following performance requirements. For our analysis we have considered primarily the resource utilization for each system, including average and peak CPU and memory utilization.

Performance MetricRequirement
Average number of CPUs per physical system2
Average CPU MHz2500 MHZ
Average CPU utilization per physical system12% (300 MHz)
Average peak CPU utilization per physical system36% (900 MHz)
Total CPU resources for all virtual machines at peak200,000 MHz
Average amount of RAM per physical system2000 MB
Average memory utilization per physical system50% (1000 MB)
Average peak memory utilization per physical system65% (1300 MB)
Total RAM for all virtual machines at peak (no memory sharing)250,000 MB
Assumed memory-sharing benefit when virtualized25% (*)
Total RAM for all virtual machines at peak (memory sharing)187,000 MB

Now we can start estimating number of ESXi hosts that is required to support the workloads.

ESXi Host CPU Specifications

Using the performance data above along with CPU and RAM requirements, it is possible to derive the high-level CPU and RAM requirements that an ESXi host must deliver. Let’s say the following table provides high-level CPU specifications details of the chosen ESXi server.

AttributeSpecification
No. of CPUs per host2
No. of cores per CPU8
MHz per CPU core2,200 MHz
Total CPU MHz per CPU17,600 MHz
Total CPU MHz per host35,200 MHz
Proposed maximum host CPU utilization80%
Available CPU MHz per host28,160 MHz
ESXi Host Memory Specifications

Similarly you need to perform analysis on high-level memory specifications. Let’s assume you have chosen an ESXi Server which comes with 96GB configuration which provides sufficient capacity for the requirements and still allow room for growth.

AttributeSpecification
Total RAM per host 96,000 MB
Proposed maximum host RAM utilization80%
Available RAM per host76,800 MB
ESXi Host Requirements

So based on the above high-level CPU and Memory specifications we can derive the minimum number of ESXi hosts required from the perspective of both CPU and Memory.

TypeTotal Peak
Resources Required
Available
Resources per Host
ESXi Hosts needed to Satisfy Requirements
CPU200,000 MHz28,160 MHz7
RAM187,000 MB76,800 MB3
VMware ESXi Hosts Required for Project

Let’s say if we anticipate the growth rate of 20%, then the following table shows the required number of hosts for our vSphere environment.

No. of ESXi hosts requiredPercentage of growth anticipatedAvailability requirementsNo. of ESXi hosts required
720%N+110

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