Author Archives: Iwan Rahabok

About Iwan Rahabok

A father of 2 little girls, my pride and joy. The youngest one quickly said "I'm the joy!"

ESXi Performance Dashboard

vRealize Operations 7.0 enhances the widgets and dashboard, which enables us to create better user experience. With that, happy to share the VMware ESXi Performance dashboard:

The above dashboard is color coded. The idea is you just need to glance that everything is green. You only need to look at the counter if they are not green.

Layout wise, it’s split into 4 levels. Do click to enlarge it as there is description added on the image. The dashboard shows Performance first, then utilization. Can you guess why?

Performance: What counters define your ESXi Performance? 

  • We know that utilization is not performance. It’s related, but it’s not the same thing. An ESXi with low utilization could be a sign of something wrong. Could it be CPU and RAM are waiting for Disk? Could it be networks are dropping packets?
  • A high performing ESXi is one that does its job well. It serves its workload easily. It’s not struggling juggling the demands from all the VMs running on it. So performance must be measured in terms of how the VMs are being served. There are 2 sub-dimension to this.
    • How bad is the problem? This covers the depth.
    • How widespread is the problem? This covers the breadth.
  • How bad is the problem can be quantified by taking the worst CPU Contention or RAM Contention experienced by all the VMs.
  • How widespread is the problem can be quantified by the percentage of VMs facing contention.
  • The 2 sub-dimensions complement each other. It gives you an insight into the performance of your ESXi. If you have a very bad contention, but it only impact a small percentage, then the problem is narrow. This could be sign of monster VMs. If the worst contention is not that bad, but it impacts almost all VMs, then the ESXi itself is struggling.
  • Do you know why I don’t add VM Disk Latency? Even on vSAN, the solution may not be on the ESXi you’re looking at.

Utilization: Drive it high as you paid for the whole box

  • Now that you can measure Performance, you have confidence to drive utilization high. No need to artificially put headroom. Hence Utilization is shown below Performance as it’s secondary.
  • For RAM, both Consumed and Active are shown. If active is low, no need to upgrade RAM as Consumed contains disk cache. For me, it’s fine for Consumed to be 95% so long RAM Contention is 0.
  • For CPU, both Demand and Usage are high. Do you know the difference between both?


  • Download the dashboard from VMware code.
  • Import the dashboard, view, and supermetric.
  • Enable the supermetric in your base policy. Hope it’s a good introduction to the awesome power of supermetric!
  • Replace your ESXi Summary Page with this. Sunny my brother has documented here.

Hope you find it useful. Next is vSphere Cluster Performance dashboard.

CPU Ready vs CPU Contention

Folks like Daniel in Hong Kong, Sajag in Thailand, and Ramandeep in US have noticed that I shifted my recommendation from CPU Contention to CPU Ready as Performance SLA. The reason is essentially Change Management. Moving from complaint-based operations to SLA-based is a transformation. It’s not something you do in a week. You need to enlighten your boss and your customers. It’s a paradigm shift that can take months.

As a result, CPU Ready is a better start than CPU Contention. Your IaaS business is not ready for Contention, pun intended.

CPU Ready is more stable than CPU Contention, as it’s not affected by Hyper Threading. Running both HT on a core reduces the amount of CPU cycle by 50%. Since HT gives only 1.25x boost, each HT gets 62.5% when both are running. That reduction is accounted for in CPU Contention, which is why it can spike to >35% when Ready is not even 1%. Test this by running 2 large VMs in 1 ESXi. If the ESXi is 16 cores 32 treads, then you run 2x 16 vCPU VM. Run both at 100%. Set Power Management to Max so you eliminate frequency scaling from impacting CPU Contention. Both should experience minimal CPU Ready but high CPU Contention. My guess is CPU Ready will be <1%, while CPU Contention will be >35%.

CPU Ready is also not affected by Power Management. As you can see here, in general you should take advantage of power savings. The performance degradation is minimal while the savings is substantial. CPU Contention accounts for this frequency drop. My guess is frequency drop of 25% will result in CPU Contention of 25%. I wrote guess as I have not seen a test.

Considering the above, Ready is a lot less volatile. This makes it more suitable as SLA. Operationally, it’s easier to implement. It’s easier to explain to folks less familiar with VMkernel CPU Scheduler.

If you use CPU Contention as formal SLA, you may be spending a lot of time troubleshooting when the business don’t even notice the performance degradation.

Where do you CPU Contention then? For advanced troubleshooting. You first check CPU Run Queue, CPU Context Switch, “Guest OS CPU Usage“, CPU Ready and CPU Co-Stop. When these 5 counters are good, and the other 3 infra element is good (RAM, Disk, Network), and you’re convinced that it’s not application issue, then you should check CPU Contention.

Hope that clarifies. If your observation in production differ to the above, do email me.

VMworld 2018 & vForum 2018 presentations

You can find my VMworld presentations here and vForum presentation here. They are in powerpoint, not PDF. Feel free to use the deck, add what’s relevant to your and remove what’s not relevant. Let me know how it helps you!

In the Advanced Performance Bootcamp, Sunny and I covered the counters in-depth. You can also find details on VM CPU and  VM RAM.

Alok and I discussed vSAN Troubleshooting in a TAM session. It’s the last session on Thursday and glad to see customers staying until the event team came in to wrap up the place. The session show how you can monitor vSAN at large. We met customers with 3500 clusters, going well beyond 10K clusters. How do you monitor such environment?

Sajag, a customer from Thailand, shared how he significantly reduce the hardware footprint (servers and storage), while improving performance. The help desk tickets went down by 40% in the last 6 months. Majority of the tickets were related to Application Team complaining on performance. His company managed to avoid purchase of new storage array and 1 blade chassis (14 Hosts) worth of hardware. More details below

Look forward to seeing you in Barcelona and Shanghai!