Virtualization

Virtualization

In computing, virtualization is a broad term that refers to the abstraction of computer resources

It is "a technique for hiding the physical characteristics of computing resources from the way in which other systems, applications, or end users interact with those resources. This includes making a single physical resource (such as a server, an operating system, an application, or storage device) appear to function as multiple logical resources; or it can include making multiple physical resources (such as storage devices or servers) appear as a single logical resource.“

Virtualization allows multiple operating system instances to runconcurrently on a single computer

Virtualization

Common Types of virtualization:

Network Virtualization

using network resources through a logical segmentation of a single physical network (e.g. Open vSwitch, KVM).

Storage Virtualization

The aggregation of multiple network storage devices into what appears to be a single storage unit.

Server Virtualization

The partitioning a physical server into smaller virtual servers.

Why we need virtualization

Reduce Data Centres footprint

Save energy, go green

Help move things to the cloud

Snapshots

Live migration

Easier management from single console

Easier High Availability (HA) deployment

Virtualization Features (Snapshots)

Snapshots:

A storage snapshot is a set of reference markers, or pointers, to data stored on a disk drive, on a tape, or in a storage area network (SAN).

Snapshot is something like a detailed table of contents, but it is treated by the computer as a complete data backup.

There are two main types of storage snapshot: copy-on-write (low capacity)

split-mirror

Virtualization Features (Live Migration)

Live migration refers to the process of moving a running virtual machine or application between different physical machines without disconnecting the client or application. Memory, storage, and network connectivity of the virtual machine are transferred from the original host machine to the destination.

Requires a shared storage

Virtualization Features (High Availability - HA)

High Availability refers to a system or component that is continuously operational for a desirably long length of time.

HA clusters or failover clusters are groups of computers that support server applications that can be reliably utilized with a minimum of down-time. They operate by using high availability software to harness redundant computers in groups or clusters that provide continued service

Virtualization Component

Hypervisor

A hypervisor is is a piece of computer software, firmware or hardware that creates and runs virtual machines.

The hypervisor manages the system's processor, memory, and other resources to allocate what each operating system requires. Hypervisors are designed for a particular processor architecture and may also be called virtualization managers.

Hypervisors types

Type 1 hypervisor (bare-metal): It works directly on the hardware of the host and can monitor operating systems that run above the hypervisor, It is completely independent from the Operating System. 

Type 2 Hypervisor (hosted): the hypervisor is installed on an operating system and then supports other operating systems above it, It is completely dependent on host Operating System for its operations.

Type 1 Hypervisor

Type 2 Hypervisor

System OS

Type1 vs. Type2 hypervisors

Server Virtualization TypesFull Virtualization: is virtualization in which the guest operating system is unaware that it is in a virtualized environment, and therefore hardware is virtualized by the hypervisor so that the guest can issue commands to what it thinks is actual hardware, but really are just simulated hardware devices created by the hypervisor.

Hardware Assisted Virtualization: is a type of Full Virtualization where the microprocessor architecture has special instructions to aid the virtualization of hardware. These instructions might allow a virtual context to be setup so that the guest can execute privileged instructions directly on the processer, even though it is virtualized.

Para-Virtualization: is virtualization in which the guest operating system (the one being virtualized) is aware that it is a guest and accordingly has drivers that, instead of issuing hardware commands, simply issues commands directly to the host operating system.

Advantages of Virtualization

Zero downtime maintenance Freedom from vendor-imposed upgrade cycles Instant provisioning Pooling hardware resource Virtual hardware supports legacy operating systems

efficiently Dynamic resource sharing Security and fault isolation Business continuity, backups, and automated

restoration

Example of the Impact of Virtualization

Before After

Virtual AppliancesTraditional Approach: A Collection of Hardware and Cables

Virtualization is Based on Insertion of a Hypervisor

on Top of Hardware

Virtual Desktop

Driving Change

Apply Virtualization to the Desktop

The Virtual Desktop Runs in a Secure Data Center

Summary Virtualization offers major savings in data center

operations.

Virtualization makes possible significant reductions in the costs of managing data centers, with simplification of systems management tasks.

Virtualization offers back-up and increased redundancy for delivery of high performance and high availability services.

Virtualization is a step in the direction of “cloud computing”.