How Resource Allocation Works in Virtual Machines



Memory allocation in a virtual machine is accomplished by its configuration; memory must be specified upon a virtual machine’s creation. This memory will represent the maximum amount of memory that the virtual server will make obtainable to the virtual machine. This memory can only be increased if the virtual machine is turned off. To control how system resources are allocated among all virtual machines that are running, the virtual server will be used. By doing this, one can allocate resources by both size and mass.  When allocating resources by capacity, one can assign the minimum and maximum percentages of the CPU resources. These resources are consumed by the virtual machine. When doing this, it is important to remember that you will only see the virtual machines that you have permission to use. Using the highest settings allows the virtual machine to never use more than the specified resources.
            By using virtual machines, one can run more than one operating system at once and benefits greater flexibility, as one can directly install, backup, reinstall, and move guest OS. Management of resources is another benefit over a regular wired setup. Virtual machines offer increased security as an intruder would have to compromise the host environment as well. Replacing a virtual machine is much more comfortable and probably cheaper than replacing a physical system. Some disadvantages of using a virtual machine can be performance drops and hardware support problems on guest OS.
            One issue that can cause more problems than a virtual machine is worth is its memory limits. When a virtual machine is transferred out of a resource pool which is effected with a memory limit, the machine can maintain those limits afterward, which are often unknown by the administrator. Due to this memory limit, virtual machines may not be able to obtain the memory that they need at a given time. Additionally, if a guest OS fails to access the memory it needs, the applications running will suffer in performance or fail to even run. By verifying the memory configuration of each virtual machine, one can find their memory limits. These limits should be compared against the actual memory that is assigned. As using many virtual machines for a task is common, this all can be a difficult experience if an automated tool isn’t used.
            There are also numerous other issues that virtual machines face. Renaming virtual machines is not possible when they are running or are hibernating. There can also be problems with copying and pasting files between the guest and host OS; the drives themselves must be shared instead. Many users often complain about difficulties closing their virtual machines when they are not responding. To accomplish this in Windows, only use the Task Manager to close the application as you would do with any program.
Tracking all the virtual machines that a user implements for their task is very necessary as multiple machines can be built quickly, and then become useless after a short period; such as in development environments. Due to this, it can be prevalent to lose track of where the virtual machines are and what they do. This causes backup problems and wasted resources. To help combat this, administrators should continuously maintain documentation of their virtual machines. Even better, implementing systems that track virtual machines is highly recommended.
“Allocating system resources to a virtual machine.” Microsoft. Web. Accessed 12 Jun 2017.



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