SLES Simplifies Server Virtualization | SUSE Communities

SLES Simplifies Server Virtualization


Server Virtualization can consolidate and increase the utilization of servers. Come see how you can lower costs with the virtualization technology built into SUSE Linux Enterprise Server.


One challenge each IT company faces is to reduce the cost of operations. Each and every penny that a company spends affects its financial results. Obviously Virtualization can help IT reduce their costs. Besides reducing costs, there are many other benefits that help companies which we will discuss now.

Virtualization is being used in many organizations to reduce power consumption, air conditioning needs, building space etc. Virtualization can simplify IT operations and allow IT organizations to respond faster to changing business needs.

Novell’s SUSE Linux Enterprise Server simplifies the task of virtualization and provides better level of efficiency to meet these demands.

This article discusses about Novell’s SLES Virtualization technology helps improve IT, and how organizations can benefit from this technology.

What is Virtualization

Virtualization is a combination of software and hardware techniques and technology that creates Virtual Machines (VMs) – computer hardware that allows a single machine to act as if there were many machines. On a physical machine–

  • Without VMs – A single OS owns all hardware resources
  • With VMs – Multiple OS’s each running independently on physical server share all the hardware resources

Figure 1 – Non Virtual Machine and VM Configurations

Click to view.

What is Server Virtualization?

One physical server, divided into multiple virtual environments, creates virtual servers. Server Virtualization is the partitioning of a physical server into smaller virtual servers. IT administrators use special software to achieve this. Instead of using a separate computer/machine for each server, many virtual servers can co-exist in one machine. This technology masks the server resources including all the virtual servers, processors and OS from server users.

Physical servers are called “Hosts” and Virtual servers are called “Guests.” Virtual servers behave like physical machines. Each system uses a different approach to allocate physical resources to virtual server needs. End users won’t be aware that they are using or connected to a virtual server at all.

Type of Server Virtualization

There are 3 types of virtual servers:

  1. Full Virtualization
  2. Para-virtualization
  3. OS-Level Virtualization

Full virtualization is done with special software called a hypervisor. It interacts directly with physical server’s CPU and disk space. It is the basic platform for Guests. It makes each virtual server run independent of each other on a machine. It monitors the physical server’s resources. For all the virtual server’s applications, it provides the necessary resources from the physical machine. A physical server hosting virtual servers must be a high-end machine capable of reserving some processing power and resources to run the hypervisor application. This can impact overall server performance and slow down other applications.

In para-virtualization, the guest systems are aware of each other. Para-virtualization hypervisors don’t need much processing power to manage guest operating systems, because each virtual server is aware of requirements from other operating systems that are requested from the physical system. The whole system works together co-operatively and as one cohesive unit.

OS-level virtualization doesn’t need any hypervisor at all. The host OS will have the required capability that performs all the functions of a fully virtualized hypervisor. The biggest disadvantage is that all the guest servers must run the same OS. Still, each guest server remains independent from all the other guest servers. But you can’t mix and match operating systems among them, because all the guest OSs must be the same. This is called an homogeneous environment.

Which method is best? This completely depends on the network administrator’s requirements. If the administrator’s physical servers all run on the same operating system, then an OS-level approach might work best. On the other hand, if the administrator is running servers on several different operating systems, para-virtualization might be a better choice. One potential drawback for para-virtualization systems is support — the technique is relatively new and only a few companies offer para-virtualization software. More companies support full virtualization, but interest in para-virtualization is growing and may replace full virtualization in time.

SUSE Linux Enterprise Server 11 includes a faster and more scalable Xen 3.3.1 hypervisor.

What is XEN?

†Xen is a virtual machine monitor for IA-32, x86-64, Itanium, and PowerPC 970 architectures. It was developed at the University of Cambridge, and is now an open source project. It allows several guest operating systems to execute on the same computer hardware concurrently. It enables you to create many virtual machines which run an instance of an operating system.

Why to Virtualize

There are many advantages of virtualization. The most popular reason for virtualization is resource utilization. A company running many servers for different purposes see only 10% utilization of each server – most of the time they are left idle. By letting several virtual servers share the hardware, a much higher average utilization rate is achieved. So, if we can use one server/system for different purposes we can effective utilize the system.

There are some other advantages besides utilization. Virtualization also makes it easier to provision and reallocate servers. Instead of having to manually set up a server, the virtualization software can set up a server using a pre-existing template and shift server images from one physical server to another to balance workloads or improve efficiency. It can also automatically set up a new virtual server on a different machine when there is a hardware malfunction. Each application is isolated from the others, which provides greater security.

Pros and Cons of virtualization:


  • Optimized usage of infrastructure

    Virtualization offers server unification that integrates various servers spread across an enterprise. This allows these servers to share applications and databases along with other infrastructure and other resources, for optimized utilization and usage of infrastructure.

  • Reduce cost of infrastructure

    A single system can host many servers, and you can remove extra servers that are no longer needed. This means you can avoid purchasing additional hardware. It also saves other resources like space needed to maintain the system, power usage costs, and extra data centres. All of which leads to significant cost savings.

  • IT management flexibility

    Virtualization requires fewer servers to perform the routine, repetitive, time consuming tasks such as configuration, upgrades, monitoring and system scheduling.

  • High accessibility of applications and data

    Virtualization so transforms the applications and data in the virtual environment that you get high accessibility without any time delays and disruption. This makes it possible for you to fulfill the needs of both customers and staff in a secure environment.

  • Improve system compliance

    For customers and partners using different OS environments and networks, virtualization makes gives great results. It can be used cross platform, across networks by overcoming the limitations imposed by OS and networks. It makes it easy for end users, customers, partners, clients to remain linked with the enterprise.

  • Easy migration of servers

    IT administrators in a company must always be ready to upgrade to the latest equipment, hardware, software, technology, etc. So whenever a new technology comes on the market, they have to migrate their servers onto that. Maintaining one single server for each need not only increases the administrators’ work, but also makes it complicated to migrate. Virtualization solves that problem.

  • Enhance reliability, scalability and protection

    Virtualization increases the scalability by decreasing the work loads of each administrator, since many servers are combined into one server and sit on one machine. The reliability of the whole system is also improved as maintaining backups for more servers is reduced. As for protection/security, the virtualization process is designed to keep virtualized resources separate.


The benefits of server virtualization are so enticing that it’s easy to forget that it has its share of limitations. You need to research the downsides carefully before opting for virtualization.

  • Bandwidth distribution

    All the virtualized servers share same bandwidth of broadband. So sometimes one server grabs more bandwidth and others get less. This sometimes decreases the reachability and usage of a server.

  • Access to I/O resources

    This is similar to the above problem. I/O devices like printers and scanners are shared among all the hosts. So, if one virtual machine is accessing the device, others are kept in the queue or may deny access sometimes.

  • Slow processing

    This problem happens when the physical server doesn’t have the capacity to meet the requirements of virtualized servers running on it. Sometimes the server’s processing power cannot meet the application needs and everything can slow down or crash.

  • Limited amount of disk space

    Too many virtual servers could impact the server’s ability to store data as there is a limited amount of disk space on a physical server.

  • Problems during migration

    As far as I know, migration of a virtual server from one physical machine to another is possible only if both physical machines use same manufacturer’s processor. If one server runs on Intel processor and other uses AMD processor, it is impossible to migrate them from one machine to other one.


*Some of the benefits of using virtualization with SLES are as follows:

  1. You will get joint customer support from Microsoft Windows server 2008 as well as from SLES running as virtualized environments.
  2. Get SAP on Linux support running XEN.
  3. Support for both Intel as well as AMD processors on servers running bother para-virtualized as well as full hypervisors.
  4. It has enhanced power management capability.
  5. Improved graphical UI
  6. Easily manageable for disaster recovery as well as load balancing using PlateSpin technology.
  7. Unlimited virtual machine support
  8. Recommended by SAP
  9. More than 2500 certified applications are supported on SLES

How is it useful for me:

Apart from the above advantages, there’s one more which I will share with you. This is from my personal experience.

I’m a software developer and have worked for different small/medium/big companies/corporations. Many companies develop their products to work in different environments — that is to work on different operating systems, in different networks, on different hardware, on different architectures etc. Corporations expect that the products on which I’m working must work on all platforms, OS’s, networks etc. But it’s quite difficult to have all the environments provided to developers.

I was provided with a good system with sufficient hard disk space, good processing speed and memory. In the system, I installed SLES and created virtualized machines where I installed different OS’s. I also need to make sure that the product I’m developing will work on different versions of the same OS. Now I can develop on one platform, move the product to other platforms which are running in VM’s and test it. If something has to be coded particular to that environment, I can make the necessary changes and continue with all the environments. This way I reduce the usage of many machines, save power, save space, save maintenance costs, and avoid needing IT staff to help me to setup the environments.

The same applies to testers also. The product that I developed will be handed over to a quality team. They must also check that it’s working fine in all conditions and environments. They will do the same by creating virtual machines and test them.

Without virtualization, my work would definitely take longer, and ultimately cost the customers a lot more.

Learn More

† Definition from
* Data collected from

(Visited 1 times, 1 visits today)

Leave a Reply

Your email address will not be published.

No comments yet