What metrics not to use

A lot of the time, we assume that some very popular metric would be better to monitor memory performance. However, many a times, it leads to something else. This means that these are not an indication of a memory performance issue. If this metric is combined with something else then it may indicate performance degradation.

In this aspect you should not use two of the most popular metrics just to understand whether memory is under pressure or not:

Let me show you what they essentially indicate.

Mem.consumed is the amount of memory consumed by one or all virtual machines. This is calculated as memory granted minus memory saved by sharing. Now the question is why we should not use this. The reason is that memory allocation will vary dynamically based on the VM's entitlement. It is important that a VM should get whatever it actually demands.

Similarly, Mem.vmmemctl is the amount of ballooned memory. This does not indicate a performance problem as well. However, when it gets combined with Host Swapping then it indicates a performance problem.

How to do it...

To spot the Consumed Memory metric value within the vSphere infrastructure, this is what you should do:

1. Open up vSphere Client.
2. Log in to the vCenter Server.
3. In the Home screen, select VMs and Templates.
4. Choose the VM where you want to monitor the Consumed Memory.
5. Go to the Performance tab on the right-hand side.
6. Select Memory from the drop-down list.
7. Click on the Advanced tab, and select Chart Options.
8. Select the Consumed metric, and then click on OK to continue.

Now you should see something similar to the following screenshot:

In this example you can see that the Consumed value of the Memhog-VM3 VM is 1409900 Kilobyte.

To understand the Mem.vmmemctl metric you should follow the Monitoring host ballooning recipe.