Posted by: Rick Vanover
Rick Vanover, VI3, Virtualization, VMware ESX
How many times have you gone back to your resource pools and wondered why your performance is not what you were expecting? Here is a quick tip on your configuration that may help understand your situation. For small- to medium-sized ESX implementations, have a uniform value for the shares for CPU and RAM on your resource pools. Modifications of the shares values can lead to issues throughout your ESX implementation if not done cautiously.
Fair Playing Field
In my experiences, when the shares are equally set – at the default values for ‘normal’ – your configurations for reservations and limits can be more correctly enforced. I’ve many times tried to grasp the concept of the shares, and this description seems to describe it best: “Consider the shares as bandwidth to use the resource reservations and limits you have set forth.” In this fashion, the limits and reservations can have the behavior you are expecting.
Do not Have Anything Set to Unlimited
While we are talking about the resource pools we should definitely mention that if you have anything set to ‘unlimited’ – you are bypassing all management of the pool. This will go for the virtual machine host resources in an unlimited fashion, and can negatively effect other guests.