VMware vSphere
VMware vSphere is the name of VMware’s server virtualization product suite. It was formerly known as VMware Infrastructure, and it consists of ESXi, a Type 1 hypervisor, vCenter Server, vSphere Client, and a few other important features that are not easily replicated on a physical infrastructure, such as vSphere vMotion and vSphere High Availability, to ensure virtual servers are up and running. Figure 18-5 shows the VMware vSphere components.
Figure 18-5 VMware vSphere Components
VMware ESXi
VMware ESXi (Elastic Sky X Integrated) is a Type 1 hypervisor that installs directly on the physical server. VMware ESXi is based on the VMkernel operating system, which interfaces with agents that run on top of it. With direct access to and control of underlying resources, VMware ESXi effectively abstracts the CPU, storage, memory, and networking resources of the physical host into multiple virtual machines. This means that applications running in virtual machines can access these resources without direct access to the underlying hardware. Through the ESXi, you run the VMs, install operating systems, run applications, and configure the VMs. Admins can configure VMware ESXi using its console or a vSphere Client. An ESXi 7.0 host can support up to 1024 VMs.
VMware vCenter Server
VMware vCenter Server is an advanced server management software that provides a centralized platform for controlling vSphere environments. It enables you to deploy, manage, monitor, automate, and secure a virtual infrastructure in a centralized fashion. You can install vCenter Server on a Windows virtual machine or physical server, or you can deploy the vCenter Server Appliance, which is a preconfigured Linux-based VM based on Photon OS with an embedded PostgreSQL database optimized for running vCenter Server and the associated services.
vCenter Server requires an extra license and serves as a focal point for management of ESXi hosts and their respective virtual machines. It correlates traffic between hosts for functionalities that span more than a single host, such as vSphere vMotion, vSphere Distributed Switch (vDS), vSphere Fault Tolerance, vSphere High Availability, and so on. Failure of a vCenter Server does not stop production traffic or affect VMs operation, but features like central management of ESXi hosts, vSphere High Availability, vSphere Distributed Switch, vSphere DRS, and vSphere vMotion are not available until the vCenter Server is restored. It is always recommended to have a redundant vCenter deployment. vCenter version 7.0 can manage up to 2500 ESXi hosts per vCenter Server and can have 45,000 registered VMs with 40,000 powered-on VMs.