VMWare vSphere – Marty Nickison II

Imagine that you are hired to help migrate 20 servers to a Microsoft Azure cloud tenet. The servers are all VMware virtual machines running on two separate 4-host clusters and are accessible via the local vSphere 6.7 install.

At the initial team meeting, everyone introduces themselves to the group. Primary assignments are distributed afterward. Your primary assignment is to compile a list of all the guests and hosts in that instance of vSphere.

Additionally, you are to compile the following information for all the guest machines (per guest):

vCPU count
Memory size
Hard Disk 1 size (primary boot drive)
Whether the most recent VMWare Tools are installed on it

You instinctively know this is nothing more than a table. You can research this data and put together a simple Excel spreadsheet with this information … you only have one problem:

WHAT IS A GUEST MACHINE?

You pull a colleague to the side at the breakfast counter before the next workday and ask them this question. You also explain you are new to VMware and are learning the terminology.

They respond with, “It can get confusing, I know. Just remember: the guests run on hosts.”

They then run … cold vegetarian omelets are not a great way to start the day, as you know from your college dorm years.

OK, WHAT IS A HOST MACHINE?

Think of it this way. Let’s imagine you have a friend over to visit your home. You are the host, and they are the guest.

The host owns most of the stuff inside the home and also the house itself (assume homeownership). The guest can gain access to many things in the host’s home, but at that moment, the guest and what they can do is limited in some way to what the host has to offer.

This is similar to guest and host machines. The host has all the resources, and the guest is utilizing the host’s resources as much as possible and as needed. In this sense, the host is the hardware, and the guest is the combined operating system and applications.

So, in short, a guest is the operating system and the things that run on it, and the host is the computer hardware and parts that the operating system is running on.

Another way to think of this is to say, “the operating system and applications (guest) are hosted on the hardware.”

Congratulations!

You have migrated the last of the servers from the datacenter into Azure VMware Solution’s Azure Private Cloud. You can see all of the migrated VMware guests listed on the new vSphere instance with three ‘virtual’ hosts load-balancing the full load of all servers that have been migrated (for now, let’s say you migrated a total of ten virtual machines). The servers are all running without operational issues in the AVS vSphere. Furthermore, you don’t see any alerts in the details tabs.

CONGRATULATIONS! YOU ARE NOT DONE!

WHAT?
WHAT GIVES?!

For anyone who plans to move into cloud migration engineering or architecture, please keep the following phase locked into your memory: “THE MIGRATION IS NOT DONE, JUST BECAUSE ALL THE SERVERS ARE MIGRATED.”

…let me explain.

Yes, getting the physical servers migrated is a major accomplishment! You should feel like a load has been lifted off of your back. However, do not be tempted to think you’ve completed your migration work just because the servers are up and running in the new environment.

Here’s the key: the migration is done when the clients are operational in the new environment.

The difference is the presence of post-migration workloads. Once the servers and related infrastructure are migrated and tested while working, you have to ensure the clients can get to the new location and that the testing results align with pre-migration results.

Specifically, the migration is done when the clients are working the way they used to before migration into the new environment with few changes to the overall work approach and execution.

Remember, we are migration engineers and architects who work to serve the clients’ needs (company, customers, etc.). IT’S ONLY WHEN THE END-USERS ARE WORKING ‘NORMALLY’ IN THE NEW ENVIRONMENT THAT WE CAN START TO CONSIDER THE CLOSURE OF THE PROJECT WITH SUCCESS.

…NEVER forget the above.