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What is a Virtual Server?

Author avatar - Jason Wynn

Jason Wynn

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Data center using virtual servers

Using virtual machines (VM) and virtual servers is no new task. We have been working with the concept of providing time-sharing solutions since the late 1960s and early 1970s. This was because the cost of using mainframe computers was extortionate and logically it made more economical sense to utilize time sharing.

With the release of massive data centers, the use of virtualization techniques has increased to make use of physical hardware. Physical servers can be bundled to create massive, aggregated pools of resources such as CPUs, memory, storage. Even aspects such as networking, and virtualization of applications are possible.

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What is a virtual server?

A virtual server replicates the same functionality as a physical server. However, multiple virtual servers can be applied to a pool of servers.  Virtual servers may be applied against a bare metal computer which allows for its operating system and interfaces to integrate into the physical server’s resources.

There are many services today that allow for a physical to virtual (P2V) server migration to occur. These can range from simple and free, to quite expensive and feature rich.

Virtual server defined

A virtual server re-creates the functionality of a dedicated physical server. It exists transparently to users as a partitioned space inside a physical server. Virtual servers makes it easy to reallocate resources and adapt to dynamic workloads. Ultimately, a virtual server is meant to make the best use of the overall physical compute resources, thus providing a better return on investment for each organization.

What are the advantages and disadvantages of virtual servers?

Virtual server advantages

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  • Reduction of cost and cost efficiencies: By partitioning physical servers and increasing the number of virtual servers running on a single box. The roles and responsibilities increase dramatically.
  • Resource isolation can occur: By supplying more than one set of services, virtual servers can be spun up quickly, development and pre-production environments can be created at a moment’s notice. The testing within independent environments ensures that things like software and development aspects don’t affect all users.
  • It’s good for the environment. The reduction of physical hardware means that it’s less likely to wind up in landfills, less likely to be running at low utilization, less likely to require upgrading constantly on a rolling lease or outright purchase. It’s cheaper and more efficient to run a well-specified server at a higher utilization than it is to run several physical servers at nearly zero.

Virtual server disadvantages

  • Spinning up virtual servers has similar limitations as a physical one, particularly if a single or a group of virtual servers are very hard working. This leads to something called resource hogging; too many servers running on a single or pool of virtual servers causes it to limit the amount of processing power available to it. The good news is that with a correctly designed solution this doesn’t occur. Correctly setting up the solution and with forethought in the design will ensure that capacity isn’t going to be an issue when your servers grow to scope the size of your business.

What are the types of virtual servers?

There are a few different methods of providing a virtual server, these are known in the industry as type-1 and type-2.  Type-1 is a native or bare-metal virtual server that runs directly on the host server’s hardware to control, manage the resources and the guest operating systems. Popular examples of this would be something like VMWare ESXi or Microsoft Hyper-V, and Oracle VM.

Type-2 is a hosted solution that runs on a conventional operating system, the same as other programs do. This means that the guest operating system runs on top of the host operating system. Examples of this are Parallels Desktop, VirtualBox, and VMWare Workstation.

Full virtualization

This is outlined above as a type-1 method. This full virtualization will run directly on the machine’s physical hardware. There isn’t an underlying operating system. This provides the virtual server with direct access to the hardware without any other software getting in the way. Because of this, system administrators and IT professionals often find that this is the most efficient way of performing virtualization. The type-1 or full virtualization is how most enterprise organizations run their virtual servers.

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Type-1 virtual servers are often more secure because the hypervisor that controls the virtualization runs directly on the physical hardware.

OS-level virtualization

This is outlined above as the type-2 method. Type 2 is sometimes called a hosted hypervisor or an OS-level virtualization. This is because the overall virtual server relies on the existing host machine’s operating system to run. This has an impact on computer resources such as processing, memory, storage, and networking resources.

You’re unlikely to see a large enterprise running type-2 hypervisors and are normally reserved for client systems or end-user systems.

These solutions are often used because the cost of entry is significantly less. Sometimes, IT professionals use type-2 virtual servers to create virtual desktops.

Para-virtualization

There is a possible third option; para-virtualization. Para-virtualization also uses a hypervisor, but the virtual servers do not fully emulate the physical host’s hardware. Instead, a para-virtualization hypervisor will take advantage of an application programming interface (API) – typically integrated into modern servers – and it directly exchanges calls to the host and virtual server operating systems. The resulting virtual servers recognize their environment as an extension of the host’s resources.

Virtual server management best practices

There are different ways to manage and maintain your virtual server but here are some of the best practices that I’ve found over the past 20 years:

  • Ensure that all the hardware used in the solution is on the hardware compatibility list for that specific version of your hypervisor.  There is nothing worse than going to a client site or working on a slow hypervisor because non-compatible hardware has been used.
  • Ensure that the hardware choice meets your minimum configuration requirements. ‘Measure twice and cut once’ is the old saying and this is very true here. Make sure that you don’t under specify the hardware required. It’s always better to have too much than too little.
  • When building virtual servers for production and enterprise systems, it’s best practice to test the memory for 72 hours to make sure there aren’t any hardware issues.
  • Always make sure your software is kept up to date. Most modern solutions will support N-1, that being N=the current version and -1 being one previous. This helps with the performance, security, and supportability of the virtual servers.

What is the difference between virtual desktop and virtual server?

Virtual desktops are the technology that allows for different operating systems to run on the same desktop, or virtual computers running on a virtual machine elsewhere for the explicit use of that one user.  An example of a virtual desktop is Citrix and Windows 365.

Virtual servers provide the ability to pool physical resources to provide a hypervisor under this infrastructure. You can have virtual desktops running on a virtual server, but it would be very rare to see virtual servers running within a virtual desktop.

Conclusion

A good place to start is getting to grip on how virtual technology works is diving straight in. To understand more about type-1 virtual servers, VMWare ESXi can be used free of charge for a period of time and built upon a magnitude of hardware to get an understanding of how the solution works.

Also, building up your knowledge of virtual networking, VMware vSphere, and completing physical to virtual migrations. If you would like to know more about how to run a type-2, Oracle VM VirtualBox provides an open-sourced hosted hypervisor that runs on a host operating system to support guest virtual machines.

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