VMware vSphere - Get the best resource usage balance across the cluster members.(6 of 10)

Within vSphere we have the ability to use Affinities.  By creating  VM to VM and/or VM to Host affinities or anti-affinities  using DRS Groups and Rules, we can keep specific virtual machines apart,  if for example they have similar resource usage patterns or together if they complement each other.  The idea is to get the best resource usage balance across the cluster members.

CPU Affinity can also be set for performance gain, whereby some virtual machines are tied to use certain host CPUs.. The problem with this approach is that it affects vMotion and migrations will fail if CPU Affinity is set.  You may also benefit from using CPU Affinity when it comes to software licensing. 

When controlling resources within a cloud environment, the providers will use the Resource Pooling functionality to perform this.  This ensures that shared resources which are available to the public domain come from a resource pool which is limited either by CPU or Memory or both.

Here is an example of a Priority Guests resource pool for CPU based on a single ESX host.

The top red line you can see is the pools limit and this is in CPU MHz.  At the bottom you can see the stat guest CPU usage in MHz, so we have a couple of virtual machines that are assigned to this priority guest resource pool and you can see that the CPU usage in megahertz line actually follows the actual usage of those stacked guests.

Now if resource pools are used for organisational purposes but are not limited, or if you have expandable reservation set, on your child resource pools only, then you will need to monitor your root resource pool.  The root resource pool is the total host capacity.

What about your critical applications? I’ll talk about that on Monday.

Jamie Baker

Principal Consultant