vSphere is the core operational software in the VxRail system. vSphere aggregates a comprehensive set of features that efficiently pools and manages the resources available under the ESXi hosts. Keep in mind that this TechBook focuses on vSphere technology specifically as it pertains to the VxRail system. Features included in other vSphere implementations may not apply to VxRail and features included in VxRail may not apply to other implementations.
VMware ESXi is an enterprise-class hypervisor that deploys and services virtual machines. The following figure illustrates its basic architecture.
Figure 28. Birds-eye view: vSphere ESXi architecture
ESXi partitions a physical server into multiple secure and portable VMs that can run side by side on the same physical server. Each VM represents a complete systemwith processors, memory, networking, storage, and BIOSso any operating system (guest OS) and software applications can be installed and run in the virtual machine without any modification.
The hypervisor provides physical-hardware resources dynamically to virtual machines (VMs) as needed to support the operation of the VMs. The hypervisor enables virtual machines to operate with a degree of independence from the underlying physical hardware. For example, a virtual machine can be moved from one physical host to another. Also, the VM’s virtual disks can be moved from one type of storage to another without affecting the functioning of the virtual machine.
ESXi also isolates VMs from one another, so when a guest operating system running in one VM fails, other VMs on the same physical host are unaffected and continue to run. Virtual machines share access to CPUs, and the hypervisor is responsible for CPU scheduling. In addition, ESXi assigns VMs a region of usable memory and provides shared access to the physical network cards and disk controllers associated with the physical host. Different virtual machines can run different operating systems and applications on the same physical computer.