Enabling agentless Guest (VM) RAM monitoring with vRealize Operations 6.3+

Agentless monitoring of the Guest RAM metrics is one of the new feature introduced with vRealize Operations 6.3 with vSphere 6.0 U1. I was really happy to finally see this functionality, as memory metrics which are provided by default are not accurate and I would say almost useless when trying to right sizing your VMs.

Active memory metric (old one) is telling you about memory which was accessed by VM during some interval, but it says nothing about real usage. Especially if you want to prevent swapping (which you should in the virtualized environments with shared storage) of the idle pages. Swapping is what will happen most of the time, if you downsize your VM based on the active memory metric only and completely ignore construct of the memory usage inside the VM.

This is where the new Guest metrics come into play, where you can see real memory usage inside VM and metrics like free memory, active file system cache, swap and so on…

However I had big troubles to get this functionality working, it was working for some hosts only in one vCenter and not at all in another.  I engaged VMware support and it tooks them “only” 4months to figure it out, but luckily they did.

1. you need to have vCenter 6.0 U1, ESXi 6.0 U1, VMware tools from 6.0U1 (this part was easy)
2. verify if you have enabled collection of the new metrics (easy part as well)
   
3. Tricky one: As those metrics are internal, its collection by vCenter is not enabled by default. In this case you need to have special permission configured for an account which you are using for connection to your vCenter:
   Performance>Modify Intervals
   according to the support this is needed only once, when you are registering vCenter Adapter. If you have your vCenter Adapter already registered you need to restart it.
   

I recommend you to check out http://virtual-red-dot.info, which is great blog about vRealize Operations.

To read more about new metrics, check out this blogpost. And to see how you can right size your VMs using them this one.

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Dusan Tekeljak

Experienced infrastructure architect and consultant with more than a decade of hands-on expertise in designing, deploying, and optimizing secure, high-performance cloud solutions across Europe and the Middle East. My focus is on VMware technologies, where I’ve led major implementations, architected mission-critical systems for telecom and finance clients, and contributed to industry knowledge as an IBM Redbooks co-author. With a collection of advanced certifications—including VCAP-DCD, VCAP-DCA, VCAP-NV, multiple VMware expert credentials—I combine technical leadership with practical delivery, consistently driving successful infrastructure transformations, operational excellence, and digital innovation for enterprise clients Opinions are my own!

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