Yellow Bricks

by Duncan Epping

io trip analyzer

vSAN IO Trip Analyzer in 8.0 Update 3 enhanced!

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Starting with vSAN 8.0 Update 3 the vSAN IO Trip Analyzer has now been enhanced! What is this enhancement specifically? Well, the IO Trip Analyzer can now also be enabled on multiple VMs at the same time. Which is especially great when you are performance troubleshooting a service that consists of multiple VMs. This enhancement allows you to monitor multiple VMs simultaneously and inspect at which layer of each of the selected VMs latency occurs. Note, this enhancements works both for vSAN ESA as well as vSAN OSA!

I created a short demo that shows this capability:

vSAN 7.0 u3: IO Trip Analyzer

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In vSAN 7.0 U1 a new feature was introduced called IO Insight. IO Insight basically enabled customers to profile workloads and it provided them with a lot of information around the type of IO the workload was producing. In vSAN 7.0 U3 this is taken one step further with the IO Trip Analyzer. The IO Trip Analyzer provides details around the, yes you guessed it, trip of the IO. It basically informs you about the latency introduced at the various stages of the path the IO has to travel to end up on the capacity layer of vSAN.

Why would you need this? This tool is going to be very useful and will complement IO Insight when it comes to doing performance troubleshooting, or when it comes to getting a better understanding of the IO path. IO Trip Analyzer can be easily enabled by going to the “Monitor” section of the VM you want to enable it for.

You simply click “Run new test” and then specify for how long you want to analyze the VM (between 5 and 60 minutes). When the specified amount has passed you simply click on “View Result” and this will then provide you a diagram of the VM and its components.

When you then click on one of the dots, you will be able to see what kind of latency is introduced on the layer. It will provide you a potential cause for the latency and it will provide you some insights in terms of how you can potentially resolve the latency. Also, if there’s a significant amount of latency introduced then of course the diagram will show this through colors for the respective layer where the latency is introduced.

Before I share the demo, I should probably mention that there are some limitations in this first release of the IO Trip Analyzer (Not supported: Stretched Clusters, CNS persistent volumes, iSCSI etc) but I suspect those limitations will be lifted with every follow-up release of vSAN. I truly feel that this is a big improvement when it comes to performance troubleshooting, and I can’t wait to see what the vSAN team is planning for the future of this release.