VMware Hypervisor

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VMware is one of the most popular solutions for data center virtualization. VMware ESX is a part of VMware vSphere (previously named VMware Infrastructure), which is a cloud OS solution that allows creating and managing pools of infrastructure of virtual PCs.

VMware ESX is a bare-metal hypervisor that makes it possible to "split up" a single server into a number of virtual machines. Since the hypervisor works directly with server hardware, it is extremely efficient at allocating resources between virtual machines and reaching peak performance.

Each virtual machine is a full-featured system with processor, RAM, BIOS, storage devices and network support, and can be used by any operating system without making any modifications. At the same time, the hypervisor itself imposes certain requirements on server hardware. To confirm that your server hardware supports VMware ESX, consult the VMware Hardware Compatibility Guide at http://www.vmware.com/resources/compatibility/search.php.

VMware's hypervisor is available in two versions: the paid ESX full version and the free ESXi version, which, if desired, can easily be upgraded to the paid version by purchasing the corresponding license. There are no differences between these two versions in functionality or virtualization features. The ESXi version, however, has not a management console for remote hypervisor management, what makes it somewhat inconvenient for corporate applications. Administrators of the full version have at their disposal a useful and timesaving tool for flexible host and virtual machine management, server consolidation, migration of virtual machines to other physical media, and more.

The key features of the VMware ESX hypervisor include:

Support for 64-bit architecture and powerful servers.

VMware supports servers with up to 64 processor cores and 1 TB of RAM. You can create up to 256 virtual processors and allocate up to 255 GB of RAM to a single virtual machine.

Dynamic server resource allocation.

The amount of resources dedicated by the host to each virtual machine can be changed dynamically, depending on what is required at any given moment. This allows achieving maximum system efficiency.

The hypervisor flexibly allocates server RAM among virtual machines, even supporting memory overcommitment, where the total amount of RAM can exceed the server's actual physical RAM. This option is transparent for virtual machine users but allows for more efficient and sparing use of server resources. Due to memory ballooning technology, server RAM that is unused by virtual machines at a given moment is reallocated in favor of resource-hungry hosts. Also supported is memory de-duplication: if memory pages used by multiple VMs are identical, then only one copy is created in the server's memory.

VMware Virtual SMP (Virtual Symmetric Multiprocessing) technology means that a single virtual machine can use up to eight physical processors simultaneously for incredible performance.

Virtual network management.

Use virtual and physical machines to build a network infrastructure of any degree of complexity, or to create virtual routers or isolate virtual network traffic. The VMs can be either on the same host server or completely different ones. Another useful feature is traffic shaping, in order to limit bandwidth for certain machines or establish a priority system.

Business application optimization.

VMware ESX and ESXi 4.0 are optimized for use with common business applications, such as Oracle Database, Microsoft SQL Server and Microsoft Exchange.

Convenience of administration.

Manage the hypervisor remotely through a graphical client, using VMware vSphere, or with a command line interface, with VMware Power (PowerCLI).

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