Virtualization Technology

Introduction

As we have learned throughout this course, virtualization technology expands the capabilities of hardware, helps control IT-related costs, while also helping to improve on a system's reliability and security. For the most part, cloud computing entails being able to access a virtual machine in order to be able to do what needs to be done just about anywhere. Put simply, a hypervisor manages such virtual machines. In effect, a hypervisor allows for having several virtual machines all working optimally on a single piece of computer hardware. Each one of these virtual machines or operating systems is able to run its own programs, as it appears that the system has the host hardware's processor, memory and resources. In reality, however, it is actually the hypervisor that is allocating those resources to the virtual machines. Hypervisors are not new to the information age arena. In fact, the first hypervisors date as far back as the 1960s, when they were introduced to allow for different operating systems on a single mainframe computer. Today, they are fundamental components of any virtualization effort. One can think of a hypervisor as the operating system for virtualized systems. It can access all physical devices residing on a server. It can also access the memory and disk, while controlling all aspects and parts of a virtual machine. This paper will examine the technical advantages and disadvantages of using a hypervisor in an enterprise, compare and contrast different types of hypervisors, as well as evaluate the effect of hypervisors on the TCO (Total Cost of Ownership) in an enterprise. Lastly, we will determine whether or not the implementation of hypervisors has an impact on system administration.

Technical advantages and disadvantages to the enterprise

Before looking at the advantages and disadvantages hypervisors introduce to an enterprise, it is first important to gain a thorough understanding of their uses and where those uses apply. Hypervisors may be used in data services for easy cloning and replication. Hypervisor-based replication also happens to be more cost effective and less complex than current replication methods, especially those involving virtual machines. Traditionally, it is very difficult to replicate virtual machines. For starters, one needs to know how to actually manage and do data replication. If a storage system-based replication method is used, the entire volume of the virtual machine needs be replicated. In the case of a lot of virtual machines running on a particular piece of hardware, a significant amount of storage is required in order to be able to store the entire volume. With hypervisor-based replication, one can choose which VMs and what parts are to be replicated, so that you could save up on storage space. Hypervisor-based replication is also hardware neutral, meaning you could store any data duplicates to any storage device.

The basic advantages and disadvantages of hypervisors are pretty much the same as in other virtualization environments. For one, server virtualization allows your client to run multiple servers on one physical computer, which translates into more efficient use of resources. Although there is some overhead, today's processors are generally more powerful than they need to be and often sit idle anyway. Your client isn't likely to notice much of a performance hit for most applications, unless they require intensive I/O operations, as databases do. This makes database servers poor candidates for virtualization.

One major advantage of the Microsoft Hyper-V type lies in the fact that it is incorporated in Windows Server 2008, meaning clients can save on licensing costs when compared with VMware's or Citrix XenServer's virtualization platforms. Since Hyper-V is also based on Windows, clients do not need to learn Linux to use it. VMware and XenServer are both based on Linux, although they can host Windows guest VMs. Moreover, there should be no arguing the fact that data services such as snapshots, cloning and replication have steadily moved out of the storage system and into the hypervisor. For example both VMware and Microsoft now include these capabilities as part of their hypervisor core. VMware now includes replication in Essentials Plus, Standard, Enterprise and Enterprise Plus versions of vSphere. Microsoft includes Hyper-V Replica in any version of Windows that incorporates Hyper-V.

Having such capabilities included with the hypervisor is an ideal option for the virtualized small to medium-sized business because it reduces cost and complexity by virtualizing the data services. Hypervisor-based data services also change the way the SMB (server message block) selects its storage hardware, and enable smaller organizations to implement disaster recovery. Features that were once important are no longer, while other features such as advanced RAID, thin provisioning, automated tiering and data protection remain.

It should be noted that replication is often an expensive add-on option from storage vendors, not to mention it requires the purchase of a second nearly identical system. Even when vendors claim to include replication, there is a cost associated with the option. There is the extra profit margin that the vendor makes on the hardware because the software is included, and there is the cost of a second storage system along with yet again the additional cost of having to support multiple replication solutions if more than one storage system is present in the data center. By using the replication in the hypervisor, costs are dramatically reduced for the enterprise. There is no extra option to purchase or "value add"- if you would, that factors in. It simply is there and ready to use.

Hypervisors in different flavors

The first hypervisor providing full virtualization was IBM's CP-40, a one-off research system that began production use in January 1967, and which became the first version of IBM's CP/CMS operating system. CP-40 ran on a one-off S/360-40 that was customized to support virtualization. Prior to this time, computer hardware had only been virtualized enough to allow multiple user applications to be run. With CP-40, the hardware's supervisor state was virtualized as well, allowing multiple operating systems to run simultaneously. CP-40 was soon re-implemented as CP-67 for the IBM System/360-67, the first production computer system capable of full virtualization. This machine included page translation table hardware for virtual memory, and other techniques that allowed a full virtualization of all kernel tasks, including I/O and interrupt handling.

Choosing the right Virtualization software for any given datacenter today is a complex task. In July 2006, Microsoft made public a free Virtual