Virtual Dedicated Servers Semi Dedicated VPS and Para virtualized VPS known as VPS VDS PVM and HVM are terms used to describe different implementations of Server virtualization technology.
Server virtualization is a technology that has been in use since the days of mainframe computing before we opted to move to the more nimble pc.
Virtualization technologies allow you to run several instances of virtual machines on an individual physical server. Isolation occurs between instances allowing for different applications and operating systems to run. The host or single physical server then performs translation between software and hardware for virtual machines through a software layer known as a hypervisor.
Detachment from the physical hardware through the hypervisor allows for easy movement of VMS between different physical platforms.
The virtual machines and the operating systems running on them are sometimes referred to as guests of the host or physical server hardware.
In a fully virtualized environment the virtual machine will function as it normally would if installed directly on the physical server.
The Hypervisor translation or hardware emulation which occurs does result in a varying loss of performance depending upon the type of virtualization platform used.
Examples of commercial and open source virtualization platforms are VMware Citrix Xen KVM Xen VitualBox OPenVZ Parallels Virtuozzo and others.
Technogenics uses VMware and Citrix XENServer for our cloud hosting solutions mainly because we require a high standard of performance from the platform aswell as a high-level of technical support from the vendors.
VPS and VDS are essentially the same thing.
Virtual Dedicated Servers are in essence fully virtualized machines which may or may not be using Para virtualized drivers.
Virtual dedicated servers do not necessarily have the features of live migration or support changes to hardware resources such as disk network CPU or ram dynamically. When Para virtualization is used for some hardware resources but not others this is known as a hybrid HVM. When the VM is fully Para virtualized this is known as a PVM.
Para virtualization and Para virtualized drivers allow a virtual machine to access physical hardware resources such as disk network and CPU directly which equates to a noticeable boost in performance.
The term bare metal speed has been used to describe the performance capabilities of Para virtualized virtual machines.
Resource pooling can be used on the physical server to share resources between virtual machines dynamically. Virtual Machines may have a set limit for dedicated resources and a second limit for burstable resources or the allowed limit the VM is able to access from the pool.
We assign dedicated resources to our cloud servers that are not shared between virtual machines unless there has been a specific request for a burstable limit.
Semi Dedicated Server is a term used to describe a scenario where the host provider agrees to limit the number of guests assigned to a specific physical server or isolated resource pool.
Cloud Servers have the benefit of Para virtualization with exclusive access to hardware resources such as ram CPU and network which can be changed dynamically in a live environment. Cloud servers can also be moved from one host platform to another at runtime which is known as Live Migration.