To provide services to the infrastructure, vSphere relies on two core components—the hypervisor, which is the virtualization layer for the complete environment, and vCenter Server, which centralizes the management of the ESXi hosts and allows administrators to automate and secure the virtual infrastructure. To complete the vSphere deployment, it is essential to know the interaction between ESXi and vCenter. Let's examine these two components to figure out their role:

• The ESXi hypervisor is the virtual platform on which virtual machines and virtual appliances run. Its main function is to provide the resources to workloads in terms of CPU and RAM. To manage the ESXi resources, ensuring performance and reliability, an additional component is necessary—vCenter Server.
• vCenter Server is a service that centrally manages ESXi hosts connected in a network and allows you to pool and manage the resources of multiple hosts. VMware vCenter Server can be installed in a virtual or physical machine with Windows Server, or deployed as a vCSA. The installation is now supported on Windows, macOS Sierra 10.12 (the installer issue due to the Sierra's security model change has been fixed with update 1), and Linux OS. Any host you plan on connecting to vCenter Server 6.5 should be running version 5.5 or above.

The vCSA is a preconfigured Linux-based (with VMware Photon OS) virtual machine that provides all services required to run vCenter Server and its components. As compared to previous versions, vCSA 6.5 has the capability of providing all services as the Windows-based vCenter Server. The latest release now integrates vSphere Update Manager (VUM) and you no longer need to install a separate Windows box. In a vSphere environment, vCenter Server is not an essential requirement to deploy the ESXi hosts, and virtual machines can run without it. However, advanced features available in vSphere can't be used without vCenter Server. You won't be able to provide services such as vMotion, Distributed Resource Scheduler (DRS), HA, FT, and Update Manager, just to mention a few.

The services required to run vCenter Server and vCenter components are now bundled in the VMware PSC, a component introduced in version 6.0 of vSphere that provides common infrastructure services for VMware products.

For a correct installation sequence, the PSC (which will be discussed later) must be always installed before deploying vCenter Server. Depending on the vSphere design, the PSC can be installed embedded in the vCenter Server or installed externally in the vCenter Server.

A correct VMware vSphere 6.5 deployment requires a specific installation sequence to avoid problems due to missing components or services and can be summarized as follow:

With a good design and following the correct workflow, the deployment procedure of vSphere 6.5 is straightforward and shouldn't raise problems. Let's have a look at the following points:

1. ESXi installation: In this step, you have to verify whether the chosen hardware platform is included in the HCL, and determine what installation method to use and which destination to use for booting the hypervisor.
2. ESXi setup: This step involves the configuration of the ESXi boot, network settings, direct console, and other settings.

3. vCenter Server and PSC deployment: You should identify what deployment model best fits in your environment for vCenter Server and the PSC. The vCenter Server can be deployed with an embedded or an external PSC depending on the design (multiple vCenter Server instances, for example). vCenter Server and the PSC can be installed on a Windows machine (physical or virtual) or on a vCSA. PSC appliances can be deployed on an ESXi host or vCenter Server instance.
4. Connect to vCenter Server: Use the integrated vSphere Web Client to complete the configuration of the vCSA or vCenter Server instance.

When the required steps are clear, let's start the vSphere deployment by examining the first core component of the infrastructure—the ESXi hypervisor.