Virtual Kim

@Kim_Bottu … Virtually Gung Ho

vSphere Cluster Calculator

I have created an excel table to calculate cluster sizes based on some variables. Take note that all values in black are VARIABLES (A total of 19 variables can be adjusted). Changing any of them will change the recommendations in the top and throughout the whole table. This is a work in progress though, potentially storage recommendations will be made as well. Check regularly to see new updates.

Download:  calculate-your-cluster-size

I have used a small trick to calculate the impact of sharing CPUs (vCPU to pCPU ratio). First I calculate the total amount (peak or average) of CPU usage in MHz and I divide that value that potentially can be the vCPU to pCPU ratio. It is not completely exact and if someone has a better idea, please let me know.

The clever thing in this table is that when the PEAK or AVG CPU load (which ever value you decide to use for your calculation, I have only one field for this) go up, the vCPU to pCPU ratio will go down and you will need more hosts. If on the contrary the PEAK or AVG CPU load goes down, the CPU consolidation Ratio line will show you a higher consolidation ratio and the table will show you when you need more or less hosts for the workloads you want to support.


  • Host amount of RAM
  • Host amount of sockets
  • Host amount of physical cores (this is not the amount of hyper-threaded CPUs!)
  • vCPU to pCPU ratio
  • MHz per core
  • Usable RAM and CPU (80% of the total amount installed RAM or CPU in MHz. You can change this value)
  • Desired number of VMs
  • Peak/Average CPU load
  • Peak/Average RAM load
  • Redundancy N+x (where x can be any number)
  • Growth per year (in % where 120% equals 20% growth, so if you need 30% growth, change the value to 130%)

Feel free to have a look and use this xls file.

Sincere thanks to Ariel Sanchez, Ahmed Ragab and Richard Diaz for their willingness to review this spreadsheet.

Recommended reads: Sean Crookston, Harley Stagner : Managing and Optimizing VMware vSphere Deployments

Also have a look at Josh Odgers wonderfull online cluster calculator:

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

Follow Virtual Kim on

Blog Stats

  • 28,237 hits
%d bloggers like this: