Virtual Private Server
Virtual private server, also known as VPS, is basically a term for marketing that is used by many Internet hosting services in reference to a virtual machine that is used only by an individual client of the hosting service. This term is used to help drive home the point that although the virtual machine is running on the same physical computer, but is software that is completely dedicated to one individual client's needs. This helps to drive home the point that individuals have all the privacy of having their site housed on a separate physical computer and can configure their virtual private server to run as a server computer would. Virtual dedicated server, also known as VDS, is not used as frequently, but is the same concept.
Every virtual server has the potential to run its very own fully operational system and can even be rebooted independently.
Splitting a single server into "partitions" so that it looks like many servers has been common on mainframe and mid-range computers for a long time. This includes the IBM AS/400. Since the inception of virtualization software and microcomputer technology, this practice has become even more common.
An Overview of Virtual Private Server
An actual physical server will run a hypervisor in most cases. This is given the job of destroying, creating and managing "guest" operating systems resources, essentially, the virtual machines. Guest operating systems are given a certain part of the total resources one physical server has, most often in a way that the guest never knows that there are any other resources other than those that have been given to it by the hypervisor.
Guest systems are usually virtualized, paravirtualized or a combination of both.
In an environment that has been completely virtualized, the guest is shown a virtualized set of hardware and has no idea that the hardware is not, in fact, physical. In cases such as this, it is the job of the hypervisor to map, translate and convert any requests that the guest system has into the correct resource requests on a host, which causes some substantial overhead. Almost every system can be virtualized by doing this, because the operating systems don't need to be changed, but CPUs that support virtualization are needed for many of the hypervisors that do full virtualization.
In an environment that is paravirtualized, the guest has a knowledge of the hypervisor and works directly with the resources of the host system, and the hypervisor uses real-time access control and division of resources. This causes performance that is near-native because the guest sees exactly the same hardware as the host and has the ability to natively communicate with it. UNIX-like systems, including Linux, some types of BSD, OpenSolaris and Plan9 are able to support this type of virtualization at this time. Installing operating systems as guests that are paravirtualized often takes an extensive knowledge about operating system in question to ensure that it can use specific hypervisor-aware devices and kernels.
What are the Uses of VPS?
Since there is often a gap between dedicated hosting services and web hosting services that are shared, virtual private servers help to bridge this. This offers and independence from other clients of the virtual private service in terms of software, but it costs much less than using a physical dedicated server. While a VPS runs its copy of the operating system it uses, clients are given superuser-level access to that particular operating system and have the ability to install almost any software that works with the operating system. Some software doesn't do well in virtualized environments including anti-virus clients, firewalls and other virtualizers. Also, some virtual private servers will place additional limitation, but they are usually fairly lenient in comparison to restrictions that shared hosting environments might have. Because there are so many virtualization customers running on one machine at a time, a VPS will usually have limitations to the RAM, disk space and processor time.
More and more companies are beginning to add virtual private server hosting, or virtual dedicated server hosting to their web hosting services. Some companies that specialize in web hosting call a VPS a Virtual dedicated server or dynamic dedicated server or vice versa. There are many obstacles to take into account when licensing proprietary software in virtual environments that have many tenants.
Virtual Private Server - From Wikipedia, the free encyclopedia
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