1.2 Understanding Virtualization

Virtualization can be used at multiple computing levels to provide services for your enterprise.

1.2.1 Where Is Virtualization Today?

Virtualization of servers and services is everywhere:

  • Virtualization with hardware, such as blade centers or Cisco Unified Computing System (UCS).

  • Virtualization with software, such as VMware, XEN, KVM, Hyper-V, and more.

  • Virtualization within the infrastructure:

    • Network: VLAN

    • SAN: port virtualization in the SAN

    • Storage virtualization

1.2.2 Why Use Virtualization?

The benefits of virtualization include the following:

  • Allows consolidation of servers to help reduce costs for hardware and power.

  • Allows independence of servers from hardware and environmental complexities and infrastructure.

  • Allows scalability of services on a single server because the hardware is more powerful than one service needs.

  • Increases server and service availability.

  • Allows you to use cloud services.

  • Builds independence from hardware to gain the flexibility of managing hardware connectivity on only the virtualization level.

1.2.3 Why Use OES Cluster Services?

The benefits are:

  • Increases service availability, minimizing recovery time when problems occur

  • Consolidation

  • Flexibility

  • Scalability

  • Manageability

  • Hardware independence

1.2.4 Server versus Service Virtualization

Virtualization can occur on different levels in the computing environment. The difference between a server and a service is summarized in Table 1-1. A server consists of hardware, an operating system environment made up of the kernel and hardware drivers, one or more services, and a process scheduler to control the services. A service consists of data and the service configuration settings, the application that provides the service (including its process, code, and executable), and a network address to give users access to the service.

Table 1-1 Server versus Service

Server with Operating System

Service

  • Hardware

  • Operating system (kernel, hardware drivers)

  • One or more services

  • Process scheduler

  • Data and configuration

  • Application (process, code, executable)

  • Network address

In a virtualized environment, a server can be virtualized as a virtual machine that is independent of the hardware. Virtualization hypervisors such as Xen, KVM, VMware, and Hyper-V allow virtualization of servers.

Figure 1-2 Virtualization Stack

With NCS, a service can be virtualized as a cluster resource that can be failed over between nodes. Clustering makes the service independent of the hardware.

Figure 1-3 Server Stack