Virtualization

Virtualization

Virtualization is defined as the abstraction of objects ("things"), creating a virtual (rather than actual) version of objects, such as an operating system, a server, a storage device or network resources.
 

For example, when you partition a hard drive into two partitions - C and D, say - you create virtual drives but the physical hard drive has not changed.

Operating system virtualization is the use of software to allow a piece of hardware to run multiple operating system images at the same time. The technology got its start on mainframes decades ago, allowing administrators to avoid wasting expensive processing power.

Similarly, Network attached storage (NAS) presents users with an abstract storage space - a single point of access to data - though in reality NAS contains many drives and tapes hidden from the end user.

In server virtualization, a software layer is inserted either directly on the physical server (host) hardware or on the host operating system. This software (also known as hypervisor or virtual machine monitor) allocates hardware resources (CPU, RAM, storage and networking) and allows a single server to run multiple operating system images at the same time. Each one of these operating systems is a `virtual server'.

Virtual machines are completely compatible with all standard x86 operating systems, applications and device drivers.

In other words, virtualization is a framework or methodology of dividing the resources of a computer into multiple execution environments, by applying one or more concepts or technologies such as hardware and software partitioning, time-sharing, partial or complete machine simulation, emulation, quality of service, and many others.

Note:==> The term "virtualization" is not always used to imply partitioning - breaking something down into multiple entities. Here is an example of its different (intuitively opposite) connotation: you can take N disks, and make them appear as one (logical) disk through a virtualization layer.

Virtualization allows higher utilization of servers, which usually run at a fraction of their capacity. By replacing physical servers with virtual ones, and consolidating many together, it is possible to reduce datacenter space, energy consumption, hardware costs and maintenance personnel. It is also easier to move virtual servers between hosts to form high availability, fault tolerant or other virtual clusters, thus improving business continuity, performance and responsiveness.

·         Without VMs: A single OS owns all hardware resources

·         With VMs: Multiple OSes, each running its own virtual machine, share hardware resources

·         Virtualization enables multiple operating systems to run on the same physical platform

Need for Virtualization/Why Virtualization: A List of Reasons

Virtualization can help you shift your IT focus from managing boxes to improving the services you provide to the organization. If you are managing multiple servers and desktops, virtualization can help you to:

Save money: Companies often run just one application per server because they don’t want to risk the possibility that one application will crash and bring down another on the same machine. Estimates indicate that most x86 servers are running at an average of only 10 to 15 percent of total capacity. With virtualization, you can turn a single purpose server into a multi-tasking one, and turn multiple servers into a computing pool that can adapt more flexibly to changing workloads.

Save energy: Businesses spend a lot of money powering unused server capacity. Virtualization reduces the number of physical servers, reducing the energy required to power and cool them.

Save time: With fewer servers, you can spend less time on the manual tasks required for server maintenance. On the flip side, pooling many storage devices into a single virtual storage device, you can perform tasks such as backup, archiving and recovery more easily and more quickly. It’s also much faster to deploy a virtual machine than it is to deploy a new physical server.

Reduce desktop management headaches: Managing, securing and upgrading desktops and notebooks can be a hassle. Desktop virtualization solutions let you manage user desktops centrally, making it easier to keep desktops updated and secure.

Resource optimization: Today's enterprise level computer resources are so powerful that they often have excess capacity. By virtualizing the hardware and allocating parts of it based on the real needs of users and applications, the available computing power, storage space and network bandwidth can be used much more effectively. Computers no longer need to be idle or performing below their capabilities because there are fewer connected users, or because the hosted application happens to be less demanding than the server can handle.

Virtual machines offer software developers isolated, constrained, test environments. Rather than purchasing dedicated physical hardware, virtual machines can be created on the existing hardware. Because each virtual machine is independent and isolated from all the other servers, programmers can run software without having to worry about affecting other applications, or external components affecting the execution of their code.

Consolidation: It is common practice to dedicate individual computers to a single application. If several applications only use a small amount of processing power, the administrator can consolidate several computers into one server running multiple virtual environments. For organizations that own hundreds or thousands of servers, consolidation can dramatically reduce the need for floor space, HVAC, A/C power, and co-location resources. This means the cost of ownership is reduced significantly, since less physical servers and floor and rack space are required, which in turn leads to less heat and power consumption, and ultimately a smaller carbon footprint.

Maximizing Uptime: Agility is all about being able to respond to changing requirements as quickly and flexibly as possible. Virtualization brings new opportunities to data center administration, allowing users to enjoy:

Ø Guaranteed uptime of servers and applications; speedy disaster recovery if large scale failures do occur.

Ø Instant deployment of new virtual machines or even aggregated pools of virtual machines via template images.

Ø Elasticity, that is, resource provisioning when and where required instead of keeping the entire data center in an always-on state.

Ø Reconfiguration of running computing environments without impacting the users.

Automatically Protect Applications from Server Failure: Server virtualization provides a way to implement redundancy without purchasing additional hardware. Redundancy, in the sense of running the same application on multiple servers, is a safety measure: if for any reason a server fails, another server running the same application takes over, thereby minimizing the interruption in service. This kind of redundancy works in two ways when applied to virtual machines:

Ø If one virtual system fails, another virtual system takes over.

Ø By running the redundant virtual machines on separate physical hardware you can also provide better protection against physical hardware failure.

Easily Migrate Workloads as Needs Change: Migration refers to moving a server environment from one place to another. With most virtualization solutions it is possible to move a virtual machine from one physical machine in the environment to another. With physical servers this was originally possible only if both physical machines ran on the same hardware, operating system and processor. In the virtual world, a server can be migrated between physical hosts with entirely different hardware configurations. Migration is typically used to improve reliability and availability: in case of hardware failure the guest system can be moved to a healthy server with limited downtime, if any. It is also useful if a virtual machine needs to scale beyond the physical capabilities of the current host and must be relocated to physical hardware with better performance.

Protect Investment in Existing, Legacy Systems: Server hardware will eventually become obsolete, and switching from one system to another can be difficult. In order to continue offering the services provided by these legacy systems, you can run it as a virtual machine on new, modern hardware, while the legacy system itself still behaves as if it were running on the same legacy hardware. From an application perspective, nothing has changed. In fact, its performance may well benefit from the newer underlying hardware. This gives the organization the time to transition to new processes without worrying about hardware issues, particularly in situations where the manufacturer of the legacy hardware no longer exists or cannot fix broken equipment.