VM Monitoring - A bit of confusion about agents

[Paul Paginton]

Hi, 

I've got a bit confused by the monitoring of Azure VMs (btw not the preview VM insights).  

In terms of monitoring agents there is the Log Analytics extension and the IaaS Diagnostic extension.  I configure log analytics as per this https://docs.microsoft.com/en-us/azure/azure-monitor/learn/quick-collect-azurevm so it picks up performance counters.  I do not deploy the IaaS Diagnostic extension.

Now when going into Azure monitor and choosing the metrics options I only see the host level metrics when I choose the VM, so it seems I can't do real time views of the guest performance counters using Azure monitor when I only have the log analytics extension installed

But if I query the logs files in Log Analytics for performance info I can see the counters for things like free disk space, processor time etc 

If I add the diagnostic extension to the VM I then have the option to see the guest performance metrics when using the metrics section in Azure monitor.

So when using only using the log analytics extension is it expected behaviour that I can only see the host level  metrics in Azure monitor for the VM?

I feel I've misunderstood something somewhere but I'm going in circles reading the documentation :)

[#2]

Naturally 5 minutes after posting I find out that yeah, to use the metrics in Azure monitor you need the IaaS diagnostic extension installed on the VM.  Just seems a bit cheeky to me as surely this means you end up paying for the data storage twice in a way, once to the storage account and again for the data into Log Analytics.  Anyway at least I get it now :)