Servers are rarely at 100% capacity. Nor should they be. But what happens to the unused resources? As a rule, nothing. Except for the fact that servers that are only two percent utilized continue to consume power for the remaining 98% that they are doing nothing. If you run multiple servers (domain controllers, file servers, database servers or other application servers), you can save yourself quite a bit ofserver hardware, and not just mathematically.Server virtualization gives you the opportunity to make better use of servers.
The previous server operating systems and applications run as virtual machines (VM) on a physical server. The interface between the virtual machines and the server hardware here is the virtualization software, the hypervisor (not to be confused with operating system-level virtualization, which does not require a hypervisor and where all guests use the same operating system). This techniquesaves not only server resources, but also energy for hardware and air conditioning. Hardware resources, such as uninterruptible power supply (UPS), can also be sized smaller. This not only helps to reduce operating costs, but also serves climate protection at the same time. Here are the system requirements for Microsoft Hyper-V on Windows Server (article from Microsoft: System Requirements)..
The biggest advantage of server virtualization is obvious: cost savings through less hardware. But this technology also offers enormous advantages in the area of administration and licensing models.
As described earlier, you need fewer resources when deploying your operating systems and applications virtually. By making efficient use of existing hardware, you not only save your company energy costs and space requirements, but also reduce expenditure on new hardware for your deployed IT infrastructure.
For example, if you want to convert an existing server from a classic hard disk system to solid state disks (SSD), this may involve a new installation or a time-consuming cloning process for physical servers. In a virtual environment, you can trigger the move of any guest systems to the new disk system via a simple selection in the virtualization host menu. This process then runs automatically in the background without affecting the availability of the servers and your applications.
Before making critical changes to a guest system (VM), you can create a snapshot of the virtual machine if required. This freezes the current state of the VM and all changes are written to a separate file. If something goes wrong as soon as the subsequent change (update or installation of a new software on the guest system) is performed, you will return to the state before the failed change in no time by applying the snapshot. In test and development environments, this can speed up processes. But even in the production environment, this could make the more costly restoration via a backup obsolete.
With Microsoft Windows Server operating systems, you have some clear cost savings when using them in virtual environments.Whereas the standard version of the server operating system may only be installed on one physical server, the license in a virtual environment allows installation on two virtual server instances (source: Microsoft product terms). Some other licensing models also offer any number of installations on a virtualization host and also simplify the activation of the operating system through an automated process.
Virtual machines consist of only a few files. A virtual hard disk that contains all the virtual machine files and a few configuration files that store the name, IP addresses and resources used by the VM. If you need to restore a virtual machine in an emergency, it's done quickly. Simply copy the files to a virtualization host on your network and start the server (though be aware of licensing requirements when moving to new hardware). There is no need for time-consuming operating system and driver installation on the new hardware. Even if your backup solution supports bare-metal recovery, problems can arise here if the new server hardware differs too much from the old system.
For planned server hardware migrations, this procedure can also be advantageous and make a time-consuming new installation (operating system and application) unnecessary..
In addition to the numerous advantages of virtualization solutions, however, there are also points that should be noted.
In server virtualization, the virtualization host (hypervisor) is the central instance that distributes the available server resources to the guest systems. If the hypervisor fails, all virtual servers running on it are also affected. Therefore, plan for this risk when server virtualization. There are also ways to minimize or completely eliminate this risk. By using several virtualization hosts in cluster operation, an automatic switchover can take place in an emergency, which even allows applications to be used without interruption.
The operating system of the hypervisor also needs an update from time to time. If there is only one hypervisor for server virtualization in your company, this can lead to problems. Deploy multiple hypervisors in your production environment so that virtual servers do not have to be shut down when an update is planned. Or operate only virtual servers that do not have mission-critical functions in the event of a failure of the virtualization host (planned or unplanned) and can also be shut down sometimes without major consequences.
On the other hand, if you operate several host systems in a cluster network, you have various helpful solutions (e.g. Cluster Aware Updating) that make the update process easier for you or even fully automate it.