vSphere Datacenter Design – vCenter Architecture Changes in vSphere 6.0 – Part 2

By Jonathan McDonald

In Part 1 the different deployment modes for vCenter and Enhanced Linked Mode were discussed. In part 2 we finish this discussion by addressing different platforms, high availability and recommended deployment configurations for vCenter.

Mixed Platforms

Prior to vSphere 6.0, there was no interoperability between vCenter for Windows and the vCenter Server Linux Appliance. After a platform was chosen, a full reinstall would be required to change to the other platform. The vCenter Appliance was also limited in features and functionality.

With vSphere 6.0, they are functionally the same, and all features are available in either deployment mode. With Enhanced Linked Mode both versions of vCenter are interchangeable. This allows you to mix vCenter for Windows and vCenter Server Appliance configurations.

The following is an example of a mixed platform environment:

This mixed platform environment provides flexibility that has never been possible with the vCenter Platform.

As with any environment, the way it is configured is based on the size of the environment (including expected growth) and the need for high availability. These factors will generally dictate the best configuration for the Platform Services Controller (PSC).

High Availability

Providing high availability protection to the Platform Services Controller adds an additional level of overhead to the configuration. When using an embedded Platform Services Controller, protection is provided in the same way that vCenter is protected, as it is all a part of the same system.

Availability of vCenter is critical due to the number of solutions requiring continuous connectivity, as well as to ensure the environment can be managed at all times. Whether it is a standalone vCenter Server, or embedded with the Platform Services Controller, it should run in a highly available configuration to avoid extended periods of downtime.

Several methods can be used to provide higher availability for the vCenter Server system. The decision depends on whether maximum downtime can be tolerated, failover automation is required, and if budget is available for software components.

The following table lists methods available for protecting the vCenter Server system and the vCenter Server Appliance when running in embedded mode.

If high availability is required for an external Platform Services Controller, protection is provided by adding a secondary backup Platform Services Controller, and placing them both behind a load balancer.

The load balancer must support Multiple TCP Port Balancing, HTTPS Load Balancing, and Sticky Sessions.  VMware has currently tested several load balancers including F5 and Netscaler, however does not directly support these products. See the vendor documentation regarding configuration details for any load balancer used.

Here is an example of this configuration using a primary and a backup node.

With vCenter 6.0, connectivity to the Platform Services Controller is stateful, and the load balancer is only used for its failover ability. So active-active connectivity is not recommended for both nodes at the same time, or you risk corruption of the data between nodes.

Note: Although it is possible to have more than one backup node, it is normally a waste of resources and adds a level of complexity to the configuration for little gain. Unless there is an expectation that more than a single node could fail at the same time, there is very little benefit to configuring a tertiary backup node.

Scalability Limitations

Prior to deciding the configuration for vCenter, the following are the scalability limitations for the different configurations. These can have an impact on the end design.

Deployment Recommendations

Now that you understand the basic configuration details for vCenter and the Platform Services Controller, you can put it all together in an architecture design. The choice of a deployment architecture can be a complex task depending on the size of the environment.

The following are some recommendations for deployment. But please note that VMware recommends virtualizing all the vCenter components because you gain the benefits of vSphere features such as VMware HA. These recommendations are provided for virtualized systems; physical systems need to be protected appropriately.

• For sites that will not use Enhanced Linked Mode, use an embedded Platform Services Controller.
  • This provides simplicity in the environment, including a single pane-of-glass view of all servers while at the same time reducing the administrative overhead of configuring the environment for availability.
  • High availability is provided by VMware HA. The failure domain is limited to a single vCenter Server, as there is no dependency on external component connectivity to the Platform Services Controller.
• For sites that will use Enhanced Linked Mode use external Platform Service Controllers.
  • This configuration uses external Platform Services controllers and load balancers (recommended for high availability). The number of controllers depends on the size of the environment:
    • If there are two to four VMware solutions – You will only need a single Platform Services Controller if the configuration is not designed for high availability; two Platform Services Controllers will be required for high availability behind a single load balancer.
    • If there are four to eight VMware solutions – Two Platform Services Controllers must be linked together if the configuration is not designed for high availability; four will be required for a high-availability configuration behind two load balancers (two behind each load balancer).
    • If there are eight to ten VMware solutions – Three Platform Services Controllers should be linked together for a high-availability configuration; and six will be required for high availability configured behind three load balancers (two behind each load balancer).
  • High availability is provided by having multiple Platform Services Controllers and a load balancer to provide failure protection. In addition to this, all components are still protected by VMware HA. This will limit the failure implications of having a single Platform Services Controller, assuming they are running on different ESXi hosts.

With these deployment recommendations hopefully the process of choosing a design for vCenter and the Platform Services Controller will be dramatically simplified.

This concludes this blog series. I hope this information has been useful and that it demystifies the new vCenter architecture.

Jonathan McDonald is a Technical Solutions Architect for the Professional Services Engineering team. He currently specializes in developing architecture designs for core Virtualization, and Software-Defined Storage, as well as providing best practices for upgrading and health checks for vSphere environments.