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.
|Average number of CPUs per physical system||2|
|Average CPU MHz||2500 MHZ|
|Average CPU utilization per physical system||12% (300 MHz)|
|Average peak CPU utilization per physical system||36% (900 MHz)|
|Total CPU resources for all virtual machines at peak||200,000 MHz|
|Average amount of RAM per physical system||2000 MB|
|Average memory utilization per physical system||50% (1000 MB)|
|Average peak memory utilization per physical system||65% (1300 MB)|
|Total RAM for all virtual machines at peak (no memory sharing)||250,000 MB|
|Assumed memory-sharing benefit when virtualized||25% (*)|
|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.
|No. of CPUs per host||2|
|No. of cores per CPU||8|
|MHz per CPU core||2,200 MHz|
|Total CPU MHz per CPU||17,600 MHz|
|Total CPU MHz per host||35,200 MHz|
|Proposed maximum host CPU utilization||80%|
|Available CPU MHz per host||28,160 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.
|Total RAM per host||96,000 MB|
|Proposed maximum host RAM utilization||80%|
|Available RAM per host||76,800 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.
Resources per Host
|ESXi Hosts needed to Satisfy Requirements|
|CPU||200,000 MHz||28,160 MHz||7|
|RAM||187,000 MB||76,800 MB||3|
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 required||Percentage of growth anticipated||Availability requirements||No. of ESXi hosts required|