ESXi

How Reversed ARP is used for MAC learning with vSphere vMotion

When a virtual machine is migrated from one ESXi host to another the traffic for that vm has to be delivered to the destination host and no longer to the source host. How is the physical switch informed about the move? ESXi sends out a Reversed Address Resolution packet on the destination host that will trigger the physical switch to update its MAC-address table. In this article I will explain how this process works and why it is important. 

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Mem.MemMinFreePct calculation example

One of the topics in the VMware vSphere Optimize and Scale course is how the amount of RAM is calculated that your host should have available as a minimum before processes such as ballooning and swapping become active.

The course material provides this table that shows us how this minimal free memory is calculated:

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vCPU and logical CPU sizing with Hyper-Threading explained

When sizing virtual machines you should be aware of the number of physical cores available in your ESXi-host and whether or not it has Hyper-Threading enabled. If you blindly follow the number of vCPU's you can add that VMware presents to you, then you could end up with VM's that offer poor performance. If you want to understand Hyper-Threading and why this is important for sizing please read the articles that I have listed at the bottom of this page.

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When did my ESXi host boot?

In the vSphere Client and vSphere Web Client you can find how many days your host has been running. But what happened before that period? How often did your host boot in the past? This information is stored in the file /var/log/vmksummary.log on your ESXi-host. The file is updated  hourly with information how long your host has been up and how many virtual machines are running at that moment.

VirtualHere with Raspberry Pi as USB server

When you want to use USB devices in a virtual machine you don't want to connect them to your physical ESXi-host and then from there pass through to a virtual machine. By doing this you pin the virtual machine to the host. For example with a failover the virtual machine would boot on another host and would not be able to connect to it's USB-device, which is still plugged into the failed host. Also with vMotion your options are limited. To solve this problem several solutions have been around to access USB-devices remotely via the network. 

Ideas for a vSphere home lab in Workstation or Fusion

In this article I would like to share a few ideas on how to setup a lab environment for vSphere. When I deliver VMware-training it is a frequently asked question by my students how they could run the software in their own lab-environment. For those who own multiple physical servers on which they can run ESXi it is not too difficult. But when your resources are limited you might need to look at other possibilities.

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