Читать книгу VMware Software-Defined Storage - Martin Hosken - Страница 7

In this book, software-defined compute refers to the compute virtualization of the x86 architecture. What is virtualization? If you don’t know the answer to this question, you’re probably reading the wrong book, but in any case, let’s make sure we’re on the same page.

In the IT industry, the term virtualization can refer to various technologies. However, from a VMware perspective, virtualization is the technique used for abstracting the physical hardware away from the operating system. This technique allows multiple guest operating systems (logical servers or desktops) to run concurrently on a single physical server. This allows these logical servers to become a portable virtual compute resource, called virtual machines. Each virtual machine runs its own guest operating system and applications in an isolated manner.

Compute virtualization is achieved by a hypervisor layer, which exists between the hardware of the physical server and the virtual machines. The hypervisor is used to provide hardware resources, such as CPU, memory, and network to all the virtual machines running on that physical host. A physical server can run numerous virtual machines, depending on the hardware resources available.

Although a virtual machine is a logical entity, to its operating system and end users, it seems like a physical host with its own CPU, memory, network controller, and disks. However, all virtual machines running on a host share the same underlying physical hardware, but each taking its own share in an isolated manner. From the hypervisor’s perspective, each virtual machine is simply a discrete set of files, which include a configuration file, virtual disk files, log files, and so on.

It is VMware’s ESXi software that provides the hypervisor platform, which is designed from the ground up to run multiple virtual machines concurrently, on the same physical server hardware.