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Use cases for Anti-Affinity VM-Host Rules

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I was in a meeting last week with Engineering and a question had come up on whether customers were actively using the Anti-Affinity (AA) VM-Host Rules capability and if so, what are some of the use cases?  We know that Anti-Affinity VM-VM Rules are used quite regularly by customers and the use cases are pretty well understood, but what is not clear was the usage and frequency of AA VM-Host rules. I figured I could help Engineering by asking some of my Twitter folllowers, the following question:

In an attempt to avoid any confusion, I also included a screenshot of the AA VM-Host Rules in the vSphere UI which you can see above. However, it looks like my attempt had failed and I actually received a number of replies that described AA VM-VM Host Rules (separate certain groups of VMs from each other, regardless of host groups), rather than AA VM-Host Rules (do not run certain groups of VMs on specific host groups). Perhaps the question could have been better phrased or it was just a simple misinterpretation, but overall it was a very useful exercise and it was great learn about all the different use cases for BOTH AA VM-VM and AA VM-Host Rules, so thank you to everyone who shared their feedback.

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Are Affinity/Anti-Affinity rules preserved during Cross vCenter vMotion (xVC-vMotion)?

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Among other things, vSphere Affinity/Anti-Affinity rules are indeed preserved with a Virtual Machine during a Cross vCenter vMotion (xVC-vMotion) which is a new vMotion capability in vSphere 6.0. If you wish to learn more about this awesome new feature be sure to read about it here and here.

There were a couple of people asking about the details on how this actually worked so I figured I would set this up in my lab and provide some additional information. In my environment I have two vCenter Server 6.0 joined to a single Platform Services Controller (same SSO Domain) which provides me with the Enhanced Linked Mode capability which is one of the requirements for a regular xVC-vMotion as it needs to be visible in the vSphere Web Client. You can also do an ExVC-vMotion, which does not require the vCenter Servers to be part of the same SSO Domain, you can find more details in this blog post here.

I initially had 3 Virtual Machines called: Web1, Web2 and Web3 which ran in my "PA-VSAN-Cluster" which is located in my first vCenter Server. I then create an Anti-Affinity rule called "Web-Rule" that ensures all three VMs are running on separate ESXi hosts. I then manually perform xVC-vMotion (remember automated DRS migration is on a vSphere Cluster boundry and will not vMotion outside of a vSphere Cluster or vCenter Server) each VM to my secondary vCenter Server to my "SB-VSAN-Cluster"

Once the VM has successfully relocated to the destination site, the Affinity/Anti-Affinity rules are then migrated over. You might be wondering why the Affinity/Anti-Affinity rule could not be created in advance and the reason is because it needs the actual VM object to be available to associate the the rules to. Once all three VMs have been migrated over, you will see that the old Affinity/Anti-Affinity rule no longer exists in the source vCenter Server and now lives in destination vCenter Server as seen in the screenshot below. Simple and elegant!

affinity-anti-affinity-rules-cross-vcenter-vmotion