Andres Rodriguez - Fotolia
The recent release of vSphere 6 comes with a small increase in resources compared to vSphere 5.x. In a production environment this will cause few problems. But it does make creating a vSphere 6 lab more of a challenge.
It is the perpetual treadmill of IT. Each new generation of hardware delivers more capacity, more CPU cores and larger RAM DIMMs. Each new generation of software demands more capacity to do more and better things than the last generation. Some software vendors like to list the lowest possible minimum hardware to avoid scaring customers. Other vendors specify a huge amount of hardware so the application is always responsive. Customers are used to increasing resource demands over time and the need to tune resource configuration. VMware's vSphere 6 has brought some changes to the minimum hardware requirements. Does this mean that new hardware is essential to upgrade?
A more needy vCenter
The most obvious increase is that the Windows installer for vCenter now demands two vCPUs and 8 GB of RAM before it will install. This is quite an increase from the previous vCenter version that did no resource checking, allowing vCenter to be installed on almost any Windows server. In anything but the smallest production environment these minimums will be insufficient for good performance.
Production vCenter servers will likely be configured with at least 16 GB of RAM to feed the Java-based services with the RAM they need. The more objects these Java services need to keep track of, the more RAM they need. This means the required vCenter Server resources will depend on the size of your environment. VMware provides the table in Figure 1 as guidance in the vSphere 6 deployment guide.
In my initial observations I have seen customers adding 50% more RAM to VMs running vCenter Server 5.x to be sure they retain performance through the upgrade to vSphere 6. This may simply be reacting to the fact that the environment has grown since they deployed the old vCenter. As the ESXi server and VM numbers increased so did the load on vCenter. I don't think any customers reassessed the CPU and RAM on the vCenter after it was deployed. The natural time to resize the VM is when they upgrade to the newest version.
Minimum ESXi unchanged
There has been no change in the minimum for ESXi 6.0 over ESXi 5.5. Two 64-bit CPUs and 4 GB of RAM are the least amount of resources needed to deploy ESXi 6.0. Naturally, any production deployment will have far more cores and a lot more RAM. I doubt you could buy a server with less than four cores, and the mainstream ones tailored for virtualization start at 12 cores. The minimums are really only important in a lab environment.
No problem in production
In a production environment, the vCenter VM will only consume a tiny fraction of the resources of the clusters that it manages. Management appliances like vRealize Operations have a greater resource demand than vCenter. Even that will be small in comparison to the total capacity of, for example, a medium-sized environment with a dozen ESXi servers. VMware engineers its management appliances not to overwhelm these medium-scale environments.
I can see some issues with small business customers -- the customers who buy the Essentials or Essentials Plus bundles and who have very modest ESXi servers. I recently looked at a customer with two ESXi servers and a total of 80 GB of RAM on those hosts. This is the sort of customer that does care about the extra 4 GB of RAM they need to upgrade vCenter. On the other hand, that same customer could upgrade the ESXi servers to 64 GB of RAM each for under $1,000. This is again a case of reassessing capacity and cost when the upgrade rolls around. The DIMMs that cost $500 a year and a half ago may cost a lot less now.
May be an issue for labs
The place where the increased minimum RAM will hurt is not in production but in non-production lab environments. Labs are used by the staff members who need to get familiar with new products before they are deployed into production. A successful production rollout is often the result of a lot of lab testing, where issues can be identified and resolved to prevent problems in production.
Most lab environments replicate only a small part of production as they have limited resources. Lab environments that were strained to replicate a vSphere 5.5 environment may struggle with the increased RAM footprint of vSphere 6.
I have seen this with my AutoLab project. With vSphere 5.5 we could just squeeze a minimal nested vSphere lab onto a laptop with 8 GB of RAM. With vSphere 6, we cannot run vCenter adequately on that machine now that 16 GB of RAM is the minimum while 32 GB is preferred for better performance.
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