Monitoring Memory - 5 Top Performance and Capacity Concerns for VMware

Memory still seems to be the item that prompts most upgrades, with VM’s running out of memory before running out of vCPU.

It’s not just a question of how much of it is being used as there are different ways of monitoring it. Some of the things that you are going to need to consider are:

–      Reservations

–      Limits

–      Ballooning

–      Shared Pages

–      Active Memory

–      Memory Available for VMs

VM Memory Occupancy

In terms of occupancy the sorts of things that you will want to look at are:

–      Average Memory overhead

–      Average Memory used by the VM(active memory)

–      Average Memory shared

–      Average amount of host memory consumed by the VM

–      Average memory granted to the VM

In the instance below we can see that the pink area is active memory and we can note that the average amount of host memory used by this VM increases at certain points in the chart.

VM Memory Performance

It is useful to produce a performance graph for memory where you can compare:

–      Average memory reclaimed

–      Average memory swapped

–      Memory limit

–      Memory reservation

–      Average amount of host memory consumed.

An illustration of this is shown below.

In this instance we can see that this particular VM had around 2.5gb of memory ‘stolen’ from it by the balloon driver (vmmemctrl), at the same time swapping was occurring and this could cause performance problems.

On Wednesday I'll be discussing cluster memory and don't forget to sign up for Jamie's free webinar on VMware memory Taking a Trip down VMware vSphere Memory Lane http://www.metron-athene.com/services/training/webinars/index.html

Phil Bell

Consultant