- Vmware Slot Size Policy Tool
- Vmware Slot Size Policy Guide
- Vmware Slot Size Policy Comparison
If no reservation is specified at the VM level, default slot size of 256 MHZ for CPU and 0 MB + memory overhead for RAM will be taken as slot size. We can control the HA slot size manually by using the following values. There are 4 options we can configure at HA advanced options related to slot size. Given this information, what is the correct slot size for the cluster? The CPU Reservation should be set to 32MHz and the memory reservation should be set to 32MB plus memory overhead. The CPU reservation should be set to 1 GHz and the memory reservation should be set to 0MB plus memory overhead. Slot Policy Admission Control With the slot policy option, vSphere HA admission control ensures that a specified number of hosts can fail and sufficient resources remain in the cluster to fail over all the virtual machines from those hosts. To see the slot size information click on the blue 'Advanced Runtime Info' link. The Slot size is calculated by the CPU and Memory Reservations at the individual Virtual Machine level in the whole cluster, the largest VM's CPU and Memory reservation determines the slot size.
This post is the follow up post for my previous post on VMware HA Slot Calculation. In that post, i have explained the step by step procedure for how to calculate the HA slot information. This post clarifies more on the Total Slots, Used Slots & Available slots in VMware HA Slot calculation. I strongly recommend to read my previous post on HA slot calculation to fully understand the concepts of this post.
Used Slots = 6
What is that? How does it calculate and our mind will think of the below calculation
Available slots = Total slot – Used slots i,e Available slots = 234 – 6 = 228. It should come as 228 as available slots but why Available slots is 150 in the above snapshot. Is that wrong or VMware did something wrong in HA slot calculation? Absolutely NOT. Below is the method of calculation for Total Slots, Used Slots & Available slots.
Available Slots = (Total Slots -Used Slots) – Slots reserved for failover capacity
How to Calculate Slots reserved for failover ?
It is basically coming from you Admission Control Policy of HA cluster. I have enabled admission control and configured Admission control Policy as ” Host Failures Cluster Tolerates” is equal to 1 . So It will make sure the resources always be available in the cluster as a reserved capacity to tolerate the 1 ESX host failure in my 3 node HA cluster.So, It has to reserve some capacity for fail over purposes.
Total Available Slots in the Cluster = 234
No of Hots in HA cluster = 3
Total Available slots per ESX host = 234 /3 = 78 Slots Per Host
“Host Failures Cluster Tolerates” Admission control Policy = 1 host Failure. So, 1 host failure should be tolerated in the cluster by reserving 78 Slots for fail over purposes.
Available Slots = (Total Slots -Used Slots) – Slots reserved for fail over by admission control policy
Available Slots = (234 – 6) – 78
Vmware Slot Size Policy Guide
Available Slots = 150 Slots
I hope this post will clear doubts regarding Total Slots, Used Slots & Available slots in VMWare HA slot calculation.
Vmware Slot Size Policy Comparison
Thanks For Reading!!!!