"Virtualization Products (Hypervisor) "
1- Xen
Xen (vendor; Citrix) is free software virtual machine monitor (hypervisor) for IA-32, x86, x86-64, IA-64 and PowerPC 970 architectures. It allows several guest operating systems to be executed on the same computer hardware at the same time.
A Xen system is structured with the Xen hypervisor as the lowest and most privileged layer. Above this layer, there are one or more guest operating systems, which the hypervisor schedules across the physical CPUs. The first guest operating system, called in Xen terminology "domain 0" (dom0), is booted automatically when the hypervisor boots and given special management privileges and direct access to the physical hardware. The system administrator logs into dom0 in order to start any further guest operating systems, called "domain U" (domU) in Xen terminology.
The Xen goes between the hardware and the operating systems of the various domains. The hypervisor is responsible for checking page tables, allocating resources for new domains, and scheduling domains. It presents the domains with a Virtual Machine that looks similar but not identical to the native architecture. It is also responsible for booting the machine enough that it can start dom0.
Just as applications can interact with an OS by giving it syscalls, domains interact with the hypervisor by giving it hyper calls. The hypervisor responds by sending the domain an event, which fulfils the same function as an IRQ on real hardware.Modified versions of Linux, Net BSD and Solaris can be used as the dom0. Several modified Unix-like operating systems may be employed as guest operating systems (domU); on certain hardware, as of Xen version 3.0, unmodified versions of Microsoft Windows and other proprietary operating systems can also be used as guests if the CPU supports Intel VT or AMD V technologies.
2- VMware
VMware (vendor; VMware, Inc.) is a software developer and a global leader in the virtualization market. VMware's desktop software runs on Microsoft Windows, Linux, and Mac OS X. VMware's enterprise software, VMware ESX Server, runs directly on server hardware without requiring an additional underlying operating system.VMware software provides a completely virtualized set of hardware to the guest operating system. VMware software virtualizes the hardware for a video adapter, a network adapter, and hard disk adapters. The host provides pass-through drivers for guest USB, serial, and parallel devices. In this way, VMware virtual machines become highly portable between computers, because every host looks nearly identical to the guest. In practice, a systems administrator can pause operations on a virtual machine guest, move or copy that guest to another physical computer, and there resume execution exactly at the point of suspension. Alternately, for enterprise servers, a feature called VMotion allows the migration of operational guest virtual machines between similar but separate hardware hosts sharing the same storage.Desktop software
VMware launched its first product, VMware Workstation, in 1999. This software suite allows users to run multiple instances of x86 or x86-64 -compatible operating systems on a single physical PC. VMware Fusion provides similar functionality for users of the Mac Intel platform, along with full compatibility with virtual machines created by other VMware products.For users without a license to use VMware Workstation or VMware Fusion, VMware offers the freeware VMware Player product, which can run (but not create) virtual machines.Server software
VMware markets two virtualization products for servers: VMware ESX Server (formerly called "ESX Server") and VMware Server (formerly called "GSX Server").VMware ESX, an enterprise-level product, can deliver greater performance than the freeware VMware Server, due to lower system overhead. In addition, VMware ESX integrates into VMware Virtual Infrastructure, which offers extra services to enhance the reliability and manageability of a server deployment. The VMware Server product offers a user interface with a similar look-and-feel to VMware Workstation.
VMware Server is also provided as freeware, like VMware Player but it is possible to create virtual machines with it. VMware Server is a "hosted" application, which runs within an existing Windows operating system, whereas VMware ESX does not depend on any host operating system - it is "bare-metal", running directly on the hardware, serving the virtualized hardware provisioned to each Virtual Machine.
3- Windows Server 2008 Hyper-V
Windows Server 2008 Hyper-V (vendor; Microsoft), the next-generation hypervisor-based server virtualization technology, allows you to make the best use of your server hardware investments by consolidating multiple server roles as separate virtual machines (VMs) running on a single physical machine. With Hyper-V, you can also efficiently run multiple different operating systems i-e Windows, Linux etc. in parallel, on a single server, and fully leverage the power of x64 computing.
Hyper-V provides a dynamic, reliable, and scalable virtualization platform combined with a single set of integrated management tools to manage both physical and virtual resources, enabling you to create an agile and dynamic data center. Hyper-V enables:
· Server Consolidation
· Business Continuity and Disaster Recovery
· Testing and Development· Dynamic Data Center
Key Features
· New and improved Architecture
· Broad OS Support
· Symmetric Multiprocessor (SMP) Support
· Network Load Balancing
· Quick Migration
· Virtual Machine Snapshots
· Scalability
See More:
- Server Virtualization
- How it Works – Server Virtualization
- Example of Server Virtualization
- Hypervisors, Xen, VMWare, Hyper-V
- Comparison of Hypervisors
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