Resource Pool Design

[manners2210]

Hi,

I was hoping to get some guidance on the best approach to take when designing resource pools as I've been tasked with looking at our existing ESXi 5.1 cluster to see if any improvements could be made...

Now, at the moment we have a common set of RPs which are High, Medium and Low which I now understand is not the ideal approach as this might not get us the expected results (Ref: http://www.yellow-bricks.com/2010/02/22/the-resource-pool-priority-pie-paradox/)  what I am looking to do is guarantee some resources to a core set of VM which provide the core infrastructure - such as the domain controllers, SQL servers etc and then ensure that our development and test VMs only get a fraction of the resources.  VMs that don't fit into these two categories will all have equal rights to the hosts resources.

I understand that resource pools only come into play when there is contention for resources.  Looking at our existing setup, we are currently only running about 30% memory consumption and about 15% CPU utilization therefore my question would be is there much benefit in creating RPs in this scenario since each VM is currently getting the amount of resources it requires?  Would it be a better idea to use reservations on the VMs themselves that I have identified as core infrastructure and if so what would be the best way of identifying an appropriate reservation for CPU and Memory?  My thoughts are that I could look at the average CPU and Mem usage over the past week/month and take an average, then use that as the reservation value?    I also hope to ensure that the cluster admission control policy which is currently set to 25% for CPU/Mem (we have four hosts) accurately reflects the amount of available capacity we have.  Its currently reporting as 98% for both which I don't believe is a true reflection.  Will using reservations for VMs help with this?

Thanks in advance

Brian

[admin]

Understanding Resource Pools in VMware vSphere

It is my experience that resource pools are nearly a four letter word in the virtualization world. Typically I see a look of fear or confusion when I bring up the topic. Even with some  http://www.yellow-bricks.com/2010/02/24/custom-shares-on-a-resource-pools-scripted/out there that discuss this topic, a lack of education remains on how resource pools work, and what they do. In this post, I’ll give you my spin on some of the ideals behind a resource pool, show off a fancy infographic, and then discuss ways to properly balance resource pools by hand and with the help of PowerShell.

Who Needs Resource Pools?

That’s a good question. You can’t even make a resource pool on a cluster unless you have DRS running. So, if your license level excludes this technology, you don’t have to worry about resource pools at all. If you are graced with the awesomeness of DRS, you may need a resource pool if you want to “weight” different types of workloads for two scenarios:

• For when memory and CPU resources become constrained on the cluster, and
• for when a workload needs a dedicated amount of resources at all times.

Now, this isn’t to say that a resource pool is the only way to accomplish these things – you can use per VM shares and reservations. But, these values sometimes reset when a VM vMotions to another host, and frankly it’s a bit of an administrative nightmare to manage resource settings on the VMs individually. I’ll give an exception to those using some sort of script, but it would require adding some creative solutions to identifying which VMs should be set to what resource values (folders, annotations, etc.).

See this: http://wahlnetwork.com/2012/02/01/understanding-resource-pools-in-vmware-vsphere/