Different Ways of Virtualization

Introduction:
What does “virtualization” or in simple terms “going virtual” really mean in today’s IT world? Virtualization is an old concept that is now being widely used for its benefits.

Virtualization can almost be applied to any and all parts of an IT infrastructure. Since virtualization is more versatile term and each of has its own significant; let’s discuss each one it in brief.

Virtualization falls into three basic categories:
Operating System
Storage
Applications.

But these categories are very broad and don’t passably outline the key aspects. It is helpful to refine these categories into eight, specific categories to thoroughly understand the differences and similarities between the definitions of virtualization.

Operating System Virtualization:
This is the most widespread form of virtualization today. Virtual operating systems (or virtual machines) are quickly becoming a core component of the IT infrastructure today. Generally, this is the form of virtualization that most of the end-users are most familiar with. Virtual machines are typically full implementations of standard operating systems, such as Windows or Red Hat Enterprise Linux, running concurrently on the same physical hardware machine. Virtual Machine Managers manage each virtual machine individually. Each operating system instance is unaware that it is a virtual and other operating system instances may be running at the same time. Companies like VMware, Intel, Microsoft, and AMD are leading the way in breaking the physical relationship between an operating system and its native hardware and extending this pattern into the data center. Data centre consolidation being a primary driving force is bringing the benefits of virtual machines to the mainstream market, allowing enterprises to reduce the number of physical machines in their data centers without reducing the number of underlying applications. This trend ultimately reduces infrastructure costs.

Application Server Virtualization:
Application Server Virtualization is often used as a synonym for advanced load balancing. The core concept of application server virtualization is best seen with an appliance or service that provides access to many different application services transparently. The virtual interface often referred to as a Virtual IP is exposed to the outside world representing itself as the actual web server, and manages the connections to and from the web server as needed. This enables the load balancer to manage multiple web servers or applications as a single instance, providing a more secure and robust topology than one allowing users direct access to individual web servers.

Application Virtualization:
While this may sound very similar; Application Server and Application Virtualization are two completely different concepts. What we now refer to as application virtualization we used to call “thin clients.” The technology is exactly the same, only the name has changed to make it more correct. One of the best examples of this includes Microsoft Terminal Services and browser-based applications. These implementations depend on the virtual application running locally and the management and application logic running remotely.

Management Virtualization:
If you implement separate passwords for your root/administrator accounts between your mail and web servers, and your mail administrators don’t know the password to the web server and vise versa, then you’ve deployed management virtualization in its most basic form. The pattern can be extended down to segmented administration roles on one platform or box, which is where segmented administration becomes “virtual”. User and group policies in Microsoft platform are an excellent example of virtualized administration rights. This is also referred as Management Virtualization.

Network Virtualization:
Network virtualization may be the most vague, specific definition of virtualization. A simple example of this is IP virtualization (VLAN): a single Ethernet port may support multiple virtual connections from multiple IP addresses and networks, but they are virtually segmented. Each virtual IP connection over this single physical port is independent and unaware of others’ existence, but the managing hardware (switch) is aware of each unique connection and manages each one independently.

Hardware Virtualization:
Hardware virtualization is very similar in concept to operating system virtualization, and to some extent it is required for virtualization to occur. Hardware virtualization breaks up pieces and locations of physical hardware into independent segments and manages those segments as separate, individual components. Although they fall into different classifications, both symmetric and asymmetric multiprocessing are examples of hardware virtualization. In both instances, the process requesting CPU time is not aware of which processor it is running on. As far as the process is concerned, it could be spread across any number of CPUs and any amount of RAM.

Storage Virtualization:
Storage virtualization can be divided into two classes:
- Block virtualization and
- File virtualization.

Block virtualization is best summed up by Storage Area Network (SAN) and Network Attached
Storage (NAS) technologies: distributed storage networks that appear to be single physical devices. SAN devices themselves typically implement another form of Storage virtualization: RAID.

File virtualization moves the virtual layer up into the more human-consumable file and directory structure level. Most file virtualization technologies sit in front of storage networks and keep track of which files and directories reside on which storage devices, maintaining global mappings of file locations. When a request is made to read a file, the user may think this file is statically located on their personal remote drive; however, the file virtualization appliance knows that the file is actually located on a server in a data center across the globe.

Service Virtualization:
Service virtualization is consolidation of all of the above into one phrase. Service virtualization connects all of the components utilized in delivering an application over the network, and includes the process of making all pieces of an application work together regardless of where those pieces physically reside. This is why service virtualization is typically used as an enabler for application availability.


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F5 WHITE PAPER - BY ALAN MURPHY