WilliamLam.com

Retrieving detailed per-VM space utilization on VSAN

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I was recently helping out my friend Paudie O'Riordan with a request from a customer who was looking for a way to collect detailed space utilization for their VMs (VM Home, VMDK & swap) running on VSAN. Today, this level of granularity is not available in the vSphere UI and the customer was interested in both the used and reserved capacity on a per-VM basis. Luckily, this information can be retrieved using the VSAN Management API.

To do so, we just need to use the VsanQueryObjectIdentities() API method, which I have used in the past to retrieve things like "thick" provisioned VM and translating VSAN Object IDs to their friendly VM display name. To retrieve space utilization information, we just need to set the includeSpaceSummary property to be true. While developing the PowerCLI sample script, I found that this specific property is currently not supported when querying vCenter Server and to retrieve this information, you must go directly to each ESXi host within the VSAN Cluster. I have already filed a feature request and it looks like this will be fixed in a future vSphere release.

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Using ESXi Kickstart %firstboot with Secure Boot

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If you install ESXi via a Kickstart script and make use of the %firstboot option to execute commands on the first boot of the ESXi host after installation, you should be aware of its incompatibility with the Secure Boot feature. If you install ESXi where Secure Boot is enabled, the Kickstart will install ESXi normally only execute up to the %post section. However, it will not execute the %firstboot scripts and if you look at the /var/log/kickstart.log after the host boots, you should see the following message:

INFO UEFI Secure Boot Enabled, skipping execution of /var/lib/vmware/firstboot/001.firstboot_001

If you have Secure Boot enabled, %firstboot is not supported. The reason for this is Secure Boot mandates only known tardisks which can hold executable scripts, and a kickstart script is an unknown source so it can not run when Secure Boot is enabled. If you wish to continue using %firstboot scripts, the only option is to disable Secure Boot and then re-enable it after the installation. A preferred alternative is to convert your %firstboot logic into an external script which can then be applied using the vSphere API (recommended method) and this way you can still customize your ESXi host after the initial installations. I have already filed an internal documentation bug to add a note regarding Secure Boot and %firstboot, hopefully that will roll out with the net documentation refresh.

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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