PAVMUG Session – Optimal Designs for vSphere 5 Licensing

The PAVMUG session on Sept 22nd, 2011 that seemed to have the second most active audience was the session where I discussed vSphere 5 licensing and some of the design considerations. There were several good questions that I would like to re-address here and share some helpful links that I promised during the session. There is a great PowerCLI script and a tool that VMware themselves offer.

You can find the presentation slides here.

Understanding vSphere 5 Licensing

In order to consider the proper design for your vSphere 5 environment, you will need to understand the new licensing model. Like vSphere 4, you will need a license for each socket in your hosts. Each edition of vSphere includes a certain vRAM entitlement for each socket as well. The vRAM entitlement gets pooled among all of the hosts managed by vCenter. You can use vCenter linked mode to extend the pool of vRAM. The amount of vRAM allocated to all of the guests in that pool (consumed vRAM) must be less than or equal to the amount of entitled vRAM. This is illustrated below:

Consumed vRAM vs. vRAM Entitlement

Consumed vRAM vs. vRAM Entitlement

 

Don’t forget: Just because a host has 128GB pRAM installed, there is overhead involved for the hypervisor and VM processes. This means that the pool will be less than the installed RAM. The “Consumed vRAM” is the total amount of vRAM that all of the guests have configured. In a guest, the configured vRAM is what you have set

Configured vRAM in a VM

Configured vRAM in a VM

 

So lets break this down a little differently. Say you have two hosts with 2 CPU sockets and 128GB of RAM. You can use two vSphere Enterprise Edition licenses for each host. An Enterprise Edition license entitles you to use up to 64GB RAM for each socket license.

vSphere Enterprise on 2 Hosts

vSphere Enterprise on 2 Hosts

 

With the two hosts, you now have a pool of 256GB of entitled RAM.

Entitled vRAM Pool

Entitled vRAM Pool

 

Now, lets say you have 20 VMs with 4GB vRAM allocated to each. That means you have 80GB of consumed vRAM. This is well below the size of the 256GB vRAM entitlement pool.

Consumed vRAM

Consumed vRAM

Since the consumed vRAM is 80GB, which is less than the 256GB entitlement pool, we are within licensing compliance. The “rules” say that you take the average consumed vRAM over a year to check for compliance. Basically, the peak consumption for each day is averaged over the previous year. This avoids having to pay for temporary VMs or small peaks in consumption.

Average vRAM Consumption

Average vRAM Consumption

Also, even though you can allocate up to 1TB vRAM to a guest, the maximum measured for compliance is 96GB per guest.

One design consideration here is to forget the old rule of “give them whatever vRAM they ask for” because the bells and whistles in vSphere will take care of things for you and not waste pRAM. The new rule is to only allocate the amount of vRAM that a workload needs to perform in an acceptable manner or you are wasting vRAM consumption. Capacity planning tools, like CapacityIQ can assist here.

So, lets compare costs. If you want a feature comparison, check out the VMware site. Here, we will just illustrate the pricing and entitlement differences. Below is an illustration of the different licensing and list pricing:

vSphere 5 Pricing Comparison

vSphere 5 Pricing Comparison

It looks like Enterprise Plus costs the most from this chart. But that is considering the old-school model of per host costs. Take a look at the per VM cost and you will be surprised. I have said before that Capacity Planner results from about 2,000 physical systems showed an average of 4.3GB of allocated RAM. So I compare per-VM costs below for 4GB and 8GB VMs.

[table “2” not found /]

What happens is that Enterprise Plus Edition costs less per VM than Enterprise Edition. Since Enterprise Plus allows for a 96GB entitlement and Enterprise allows for a 64GB entitlement, the cost per vRAM entitlement is lower, so the cost per VM is lower. This is another design consideration because you may only want the features associated with Enterprise Edition, but Enterprise Plus Edition costs less per VM and offers some nice features. A capacity planning study would need to be done to figure out your cost per VM because it WILL be different.

So, I took a recent Capacity Planner study and fed it some hypothetical information for the ESXi hosts. The consolidation scenario has 187 physical machines that are candidates for virtualization. For the target hosts, I tried a scale out model using a two socket servers with 128GB and 192GB RAM and and a scale up model using four socket servers with 256GB and 384GB RAM so that they fit into the Enterprise Edition and Enterprise Plus Edition entitlements. In these instances, the scenarios called for eight two-way or six four-way hosts. Obviously, there was plenty of pRAM available for all four scenarios. So, now, when we compare costs per VM, the prices change:

[table “3” not found /]

Figuring Out Licensing Compliance

There are a few tools that will assist you with determining the licensing you will need to stay compliant to the new rules. Check out Virtual-Al’s post and his accompanying PowerCLI script to validate licensing.

VMware has posted their own tool to determine licensing as well. Download the installer and set it up on a Windows Machine. You will need to have the JVM installed as well.

Licensing Advisor Help Page

Licensing Advisor Help Page

Licensing Advisor Login Page

Licensing Advisor Login Page

Licensing Advisor Report

Licensing Advisor Report

 

There is also a compliance reporting tool within the vSphere 5 vCenter Server, so you can use the client to check your licensing. Once you have vSphere 5 vCenter Server installed, make sure to also install the vSphere Web Client Server, which is required for the licensing reports to work properly.

vSphere Web Client Server

vSphere Web Client Server

 

Below are some screen shots of the licensing reporter as viewed from the vSphere Client:

vSphere Licensing Reporter Showing vCenter Licenses

vSphere Licensing Reporter Showing vCenter Licenses

 

vSphere Licensing Reporter Showing CPU Licenses

vSphere Licensing Reporter Showing CPU Licenses

vSphere Licensing Reporter Showing vRAM Entitlement

vSphere Licensing Reporter Showing vRAM Entitlement

 

vSphere Licensing Reporter Showing Alert Threshold Setting

vSphere Licensing Reporter Showing Alert Threshold Setting

 

Conclusion

Make sure you assess the performance of your environment to make sure you allocate the proper amount of vRAM for each guest. Once you have figured our your consolidation scenarios for each CPU and pRAM configuration, calcualte the costs per VM or even cost per vApp. Create a design based on your findings and then implement the design. Monitor the performance of the new environment to make sure your performance is equal or better than the original.

 

 

 

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