Whether we talk about any of these, virtualization always aims for the same: easier administration, better valuation of the hardware, more flexible business support and lower running costs.
Among various sorts of virtualization technologies the currently most significant one is server virtualization using Intel platform and Windows operation system (the so-called WINTEL platform). It is obvious - while mainframes and midrange servers have been using this technology for a relatively long time, none of the producers of WINTEL servers has developed a mainstream virtualization technology. This is especially surprising as there is great potential for virtualization - in average company there number of WINTEL servers exceeds the number of the other systems (UNIX, iSeries, zSeries) by an order or two and is growing.
A bit of history...
The reason why virtualization on this platform has only been in spotlight for two years was the suspicion on the market. Such a tool means creating an interlayer between the physical hardware and the operating systems which can have impact on reliability and performance of the systems. Moreover, there were concerns whether Microsoft, as the developer of the operating system, would support such configuration. Despite all this, mid-sized and small-sized companies have been discovering the advantages of virtualization and started using it for their critical systems. Even though there were various developers of virtualization tools, there was just one solution that gained the status of a widespread standard - the solution by VMWARE. Still, most of the major customers were waiting to hear the experience of the others and Microsoft's reaction. Finally, two years ago Microsoft bought a virtualization technology, developed it and now supplies it at as Windows 2008 server component - the so-called Hyper-V. Both solutions are now perceived as standards. VMWARE has more experience with virtualization and, as it specializes on this field, is a bit ahead technologically. On the other hand, Microsoft has the advantage of its position on the market and the ability to push their product through and the product has proved useful and functional with many customers.
Both virtualization platforms are well tested, so both the developers now focus on additional products. Various researches (e.g. mValent Survey: IT Execs Say Middleware is a 'Time Sink', 08/26/2008, where 300 senior IT professionals were inquired) have shown that virtualization itself does not make administration easier but it renders it at least equally complex (13.4% of the senior IT specialists) or even more complex (26.9%). That is why both VMWARE and Microsoft continue to develop tools for virtualization management. Today there are tools virtual server lifecycle management, tools for easy administration of testing environments (with support for versioning and rollbacks to previous versions), tools for efficient backup... All this proves that virtualization may be implemented in enterprise environments as well.
Motto: The term "virtualization" is a new phenomenon in today's world. We talk about virtualization on hardware level or using special software, operating systems are virtualized and so are applications. Whether we talk about any of these, virtualization always aims for the same: easier administration, better valuation of the hardware, more flexible business support and lower running costs.
The possibilities of virtualization
Customers have gained trust in virtualization over the last few years and started to look into this area intensively. The following paragraphs provide a brief overview of basic types of deployment and explain why virtualization is useful.
In the past, virtualization was most commonly used in testing and development environments. Virtual platform is an optimal tool for these tasks thanks to the possibility to save the current server state, launch a new version of an application or to return to the previous state if it is not working. Other advantages include the possibility to create a new virtual server easily, to alter its computational capacity just by changing the parameters and to close the server down after the project is finished. These features have made development and management of these environments substantially easier.
Renewal of old hardware was another common ground for virtualization. Typically when the server maintenance contract had ended, the server was replaced by a new one, which required time-consuming and costly re-installation of the applications. Some applications required an older operating system which could not have been installed on the new hardware. Virtualization without necessary re-installation solves both these problems.
The most important benefit of virtualization is probably the possibility to consolidate server hardware infrastructure. WINTEL is the fastest growing platform based on the number of the devices used. The result of this trend is a growing demand on data center capacity. Even though hardware producers react by reducing the size of the servers and selling blade servers, the data centers are getting more and more crowded and their capacity is insufficient (this is not just a question of physical space but also of other parameters such as power requirements, cooling, UPS or network capacity). As the performance of the new types of servers increases, it is now possible to run up to (on average) 15 virtual servers on a single machine and thus reduce the number of devices in data centers significantly.
However, for two reasons there still were some doubts as to whether this problem can be solved by virtualization: the risk of necessary overhead of the virtualization layer and possible outage of the physical server. Server outage and subsequent recovery is critical as it also causes outage of all the virtual servers running on it. The first problem was solved over time with increased hardware capacity. The second problem is solved by the virtualization layer itself. When the outage of the physical server occurs, the virtualization layer rearranges the virtual machines onto other nodes and restarts them. When the virtualization layer is reliable enough, it opens door towards consolidation of WINTEL servers in the data centers.
Even though virtualization is technically a part of infrastructure and as such has the effect especially on efficiency and flexibility of IT operations, there is also direct impact on business - it provides so-called virtual hardware storage. By introducing a single physical server into the virtualization infrastructure, the IT gets capacity for several common projects. The so-called staging area is created on the virtualization technology that works as a temporary buffer. In case a project needs another server or more capacity, one does not have to wait 4-6 weeks for the delivery but can use the capacity of the staging area. Once the production capacity is sufficient, the virtual servers are simply moved to a different cluster and the staging area is freed again. This allows for immediate supply of computational capacity for business projects, better usage planning of the existing physical servers and it also makes the company almost independent on the delivery period. The shared capacity of the virtual infrastructure is then billed onto the project in the same way the physical servers would be.
The above mentioned aspects are the most notorious advantages of virtualization, however, it has other interesting impacts, such as the possibility to choose hardware manufacturer independently. Company dependency on a single hardware manufacturer has been a common problem. IT department uses certain tools and processes for server lifecycle management so that it works flexibly and efficiently. Some tools are hardware-specific, others are platform-independent but they still require different configuration based on server manufacturer. Example: the tool that allows the administrator to take over the screen once the server is turned on and that is essential in any remote control scenario is specific for each server manufacturer. Another example: it is possible to use a general-purpose tool but the file containing hardware information (that must be monitored as well) has to be accessed in various ways. The IT department is restrained by the existing tools to such extent that it actively opposes any change to avoid the need to solve what has already been solved. As a result, the IT department refuses to organize such tenders. As a positive effect of virtualization, even when the hardware platform is changed all the servers work without the need to be reconfigured. Thus, if a company decides to change server brand, all the existing tools and processes connected with virtual servers remain functional without the need for modifications.
Another interesting effect is that high availability is gained even for applications that do not deal with availability themselves. A properly designed virtualization platform is protected against collapse of one or more physical servers (as described above) by the ability to "pick out" the affected virtual computers and restart them. Eventual downtime can be measured in seconds (compared to hours as in case of non-virtualized servers). As the high availability is solved on the virtualization platform level, it affects all the related virtual servers. However, the solution is also useful for systems and applications that already provide high availability. The price of the high-availability application is substantially higher than a standard license and using a virtualization platform can do the same for less.
The trends of today
Today it is already clear that the answer to the question as to whether to virtualize and what to virtualize can, with just a little exaggeration, be "anything that can be virtualized should be virtualized". Of course the environment is always company-specific but our experience shows that most of the WINTEL systems can be operated as virtual servers. There certainly are restrictions - technological, operational or economic. For example, current virtualization technologies do not support emulation of more than four CPUs or do not support some kinds of peripherals. Still, practical experience suggests that 90% of the servers of a typical customer can be virtualized.
Feasibility study we have done for one of our customers (enterprise environment, data centers, SAN infrastructure) proves it. The study focused on virtualization possibility of approx. 70 servers with ending hardware support. In the end only 4 of the servers proved not suitable for virtualization. As a part of this study, business case was prepared for three alternatives - virtualization, switch to new HW or purchase of prolonged support. When data center running costs were included in the calculation together with the costs of eventual reinstallations and the price of the new HW and its maintenance was calculated, virtualization proved to be approx. 20% cheaper than number two option (new hardware).
To those who wait to see if VMWARE keeps its position or if Microsoft gets ahead, we would only want to recommend thinking it through but making a decision. The race is not won and will not be for a long time. However, both solutions already are stable and operational and both companies plan to support and develop their current solutions. It is not likely that one or the other developer would come up with such an innovation that would grant him immediate and substantial technological advantage in the next four years. Both solutions are going to coexist and supposedly tools will be developed for mutual conversion of the virtual servers between them. Today, to hesitate means to postpone the discovery of what virtualization can bring.