VMware has recently published 3 new videos. I wanted to point to the third one which is very good for understanding the very interesting topic about slot size and admission control. If you ever wondered what does exactly that HA cluster policy called “Host failures the cluster tolerates” or how to understand slot size calculations,  than this video will brings you all the answers.

Admission control policy based on host failures the cluster tolerates uses slot based reservation, so the good understanding of how those slots calculations works is crucial. You can see an example on the image below on how those slots are calculated and then see how many host failures cluster can tolerate. A slot size takes into account the largest combination requirements of memory and CPU per VM.

In this example you’ll see that the current failover capacity is 1. So if the admin setup the failover capacity to 2, additional VMs can’t be powered On. You can click to enlarge.

Follow the video for explanation.

This video is great resource to understand slot sizes calculations.

The two other videos are:

• Roles, Privileges and Permissions in the vSphere Web Client
• vSphere HA Admission Control

My vSphere 5.5 page got recently few more articles. Check it out!