Myths about technology are often difficult to burst, and few are more trying than those concerning server virtualization.
Virtualization has an ever-growing worldwide fan base, but it is not without its detractors. Those who oppose server virtualization are quick to tick off a list "problems" with the technology. These 10 myths perpetuate suspicion and paranoia for those considering a switch to a virtual infrastructure. Some of these myths were true a few short years ago but have since been put to rest by better technology, mature software and vendor competition.
1. Server Virtualization Is Too Expensive
Some server virtualization solutions are more expensive than others, but some solutions, such as Red Hat's Enterprise Virtualization (RHEV), have fixed, predictable subscription costs that take the uncertainty out of budget concerns and projections. Often, the primary goal of virtualization is to save money by leveraging high-end hardware using multiple virtual systems to spread the costs among those systems. Server virtualization will save money, if executed correctly. Correct execution involves careful planning and prudent technology selection.
2. Virtual Machines are Less Secure
Security concerns abound when speaking of virtualization. The truth is virtualization is no more or less secure than other server-based technologies. It's certainly no less secure than physical server systems. Some negative rhetoric originates from virtualization's need for a host OS. Typical host OSes are bare bones Linux installations for which you have to manually set up Secure Shell (SSH). This means the host OS is very secure since it runs few, if any, standard network services.
3. Reported Consolidation Ratios are Bloated
This myth depends on the type of virtualization method you're discussing and what numbers you've had quoted to you. A realistic consolidation ratio of underutilized physical systems to appropriately sized and utilized virtual systems is 3-to-1. The 3-to-1 ratio refers to fully virtualized systems, not container-type virtualization where ratios can exceed 10-to-1. When considering virtualization, consolidation ratios are but one statistical pixel in virtualization's big picture.
4. Server Virtualization is Difficult to Learn and Support
Virtualization leverages standard skill sets from enterprise support staff: Linux, Unix and Windows services change little in a virtual infrastructure. The skills required to support a physical environment easily transfer to the new virtual environment. Virtualized OSes behave much like their physical counterparts.
5. Server Virtualization Complicates System Management
Virtualized infrastructures, by design, are less complicated than their physical cousins. A single management interface comes standard with any virtual platform. From this single interface, an administrator can view system consoles, create backups, reboot or shut down systems, change hardware and fully manage dissimilar OSes.
6. Applications won't Migrate to Virtual Machines
If your applications run today on a physical server, they'll run on a virtual server. Red Hat is one company that guarantees successful physical to virtual migration for applications. Applications rarely connect directly to hardware resources in such a way that would make them unusable on a virtual machine.
7. Virtual Machines Exhibit Lackluster Performance
This entry might not have made the myth list a few years ago, but technology has caught up to virtualization's hype. High performance disks and controllers, virtualization-enhanced CPUs, gigabit Ethernet and storage-area network devices place this assertion firmly in the myth column. Additionally, virtualization software has improved to the level that virtual machine performance rivals that of physical machines.
8. Lengthy Recovery Times for Virtual Machines
Like any well-executed backup and recovery plan, virtual machine recovery depends on the people who implemented the plan. Virtual machine restore procedures offer quick recovery compared to that of the fastest tape-based system. Often, physical systems require a complete OS reinstall and application restore. This process can take hours. Alternatively, virtual machine recovery requires a simple replacement of the damaged virtual disk files with undamaged ones. Service restoration can take as little as a few minutes. Some administrators choose to use traditional backup technology with virtual machines that may prolong this effort. However, that choice has nothing to do with virtualization itself.
9. Server Virtualization Leads to Server Sprawl
Server sprawl refers to the practice of creating virtual machines that consume virtual host resources with low return for those resources. It is neither a natural progression nor a result of using virtual infrastructure. Server sprawl has more to do with administrative control and policy breakdown than the technology it's based on, and it happens just as often in physical environments.
10. Server Virtualization Creates Licensing Problems
This myth sprang from the same dungeon as the server sprawl one. It refers to the idea that virtual machines would allow renegade administrators to use too many licenses for a particular product and place their companies at legal risk. Virtual machines are subject to the same constraints as physical machines. For example, Windows systems must perform license activation via the Internet or the system software expires out after a trial period and ceases to operate without proper license activation.
Ken Hess is a freelance writer who writes on a variety of open source topics including Linux, databases, and virtualization. He is also the coauthor of Practical Virtualization Solutions, which is scheduled for publication in October 2009. You may reach him through his web site at http://www.kenhess.com.
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