Author Archives: Ravi Soundararajan

Ravi Soundararajan

About Ravi Soundararajan

Ravi Soundararajan is a Principal Engineer in the Performance Group at VMware. He works on vCenter performance and scalability, from the UI to the server to the database to the hypervisor management agents. He has been at VMware since 2003, and he has presented on the topic of vCenter Performance at VMworld from 2013-2017. His Twitter handle is @vCenterPerfGuy.

Writing Performant Tagging Code: Tips and Tricks for PowerCLI

vSphere 5.1 introduced an inventory tagging feature that has been available in all later versions of vSphere, including vSphere 6.7. Tags let datacenter administrators organize different vSphere objects like datastores, virtual machines, hosts, and so on. This makes it easier to sort and search for objects that share a tag, among other things. For example, you might use tags to track a group of VMs that all have the same operating system.

Writing code to use tags can be challenging in large-scale environments: a straightforward use of VMware PowerCLI cmdlets may result in poor performance, and while direct Tagging Service APIs are faster, the documentation can be difficult to understand. In this blog, we show some practical examples of using PowerCLI and Tagging Service APIs to perform tag-related operations. We include some simple measurements to show the performance improvements when using the Tagging Service vs. cmdlets. The sample performance numbers are for illustrative purposes only. We describe the test setup in the Appendix.

Update: There is also a  white paper on this topic, which references this blog. See VMware vSphere 6.7 Tagging Best Practices.

1. Connecting to PowerCLI and the Tagging Service

In this document, when we write “PowerCLI cmdlets,” we mean calls like Get-Tag, or Get-TagCategory. To access this API, simply open a PowerShell terminal and log in:

Connect-VIServer <vCenter server IP or FQDN> -User <username> -Pass <password>

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vCenter performance improvements from vSphere 6.5 to 6.7: What does 2x mean?

In a recent blog, the VMware vSphere team shared the following performance improvements in vSphere 6.7 vs. 6.5:

Moreover, with vSphere 6.7 vCSA delivers phenomenal performance improvements (all metrics compared at cluster scale limits, versus vSphere 6.5):
2X faster performance in vCenter operations per second
3X reduction in memory usage
3X faster DRS-related operations (e.g. power-on virtual machine)

As senior engineers within the VMware Performance and vSphere teams, we are writing this blog to provide more details regarding these numbers and to explain how we measured them. We also briefly explain some of the technical details behind these improvements.

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vCenter 6.5 Performance: what does 6x mean?

At the VMworld 2016 Barcelona keynote, CTO Ray O’Farrell proudly presented the performance improvements in vCenter 6.5. He showed the following slide:


Slide from Ray O’Farrell’s keynote at VMworld 2016 Barcelona, showing 2x improvement in scale from 6.0 to 6.5 and 6x improvement in throughput from 5.5 to 6.5.

As a senior performance engineer who focuses on vCenter, and as one of the presenters of VMworld Session INF8108 (listed in the top-right corner of the slide above), I have received a number of questions regarding the “6x” and “2x scale” labels in the slide above. This blog is an attempt to explain these numbers by describing (at a high level) the performance improvements for vCenter in 6.5. I will focus specifically on the vCenter Appliance in this post.

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