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VMware Inc., a Wholly Owned Subsidiary of EMC Corporation , is a major vendor of Virtualization software for X86 -compatible computers, including '''VMware Workstation''' and the Freeware '''VMware Server''' and '''VMware Player'''. The company is based in Palo Alto , California , United States . PRODUCTS VMware Workstation VMware Workstation software consists of a Virtual Machine suite for Intel X86 -compatible computers which allows the creation and execution of multiple x86 virtual computers simultaneously. Each virtual machine instance can execute its own guest Operating System , such as (but not limited to) Windows , Linux , and BSD Variants . In simple terms, VMware Workstation allows one physical machine to run numerous operating systems simultaneously. Other VMware products help manage or migrate VMware virtual machines across multiple host machines. VMware Workstation has grown in popularity due to the large number of servers proliferating in the corporate setting. Transferring workstations and servers to the Virtual Machine environment allows for easier management, a reduction in footprint and greater redundancy. VMware Player on Windows XP ]] VMware Player is a free virtual machine host. It is able to run virtual machines made by other VMware products, but the Player is unable to create new virtual machines. There are many free virtual disk images of operating systems on the website; many of which are community made. There are also freeware tools for creating VM's, mounting, manipulating and converting VMware disks and floppies, so it is possible to create, run and maintain virtual machines for free (even for commercial use). VMware Server VMWare released VMWare server on February 6, 2006. VMware Server is another virtual machine host, presently in Beta . VMware Server can create, edit, and play virtual machines. In addition to the ability to run virtual machines created by other VMware products, it can also run virtual machines created by Microsoft Virtual PC. Due to intense competition in the virtualization market, VMware Server is being freely distributed in the hope that users will eventually upgrade to VMware ESX Server. {Link without Title} VMware ESX Server VMware ESX Server is quite different from the other VMware products - which all run on top of either Windows or Linux - as it has its own proprietary kernel and is installed directly on the bare metal. This approach provides better control and granularity on allocating resources to Virtual Machines, and also increases security, thus positioning VMware ESX as an enterprise-grade product. ESX is VMware's flagship product and has been rapidly adopted by companies who are looking to consolidate their servers. Two other products are used in conjunction with ESX - Virtual Center and VMotion. Virtual Center allows monitoring and management of multiple ESX or GSX servers. VMotion allows moving virtual machines between servers on the fly, with zero downtime. See the VMware Products page for more products by VMware. DESCRIPTION The computer and operating system instance that executes the VMware Workstation process is referred to as the host machine. Instances of operating systems running inside a virtual machine are referred to as guest virtual machines. Like an Emulator , VMware Workstation provides a completely virtualized set of hardware to the guest operating system—for example, regardless of make and model of the physical network adapter, the guest machine will see an AMD PCnet network adapter. VMware virtualizes all devices within the virtual environment, including the video adapter, network adapter, and hard disk adapters. It also provides pass-through drivers for USB, serial, and parallel devices. Because all guest virtual machines use the same hardware drivers regardless of the actual hardware on the host computer, virtual machine instances are highly portable between computers. For example, a running virtual machine can be paused, copied to another physical computer, and unpaused to resume execution exactly where it left off. With VMotion, a new feature in VMware's VirtualCenter, it is no longer even necessary to pause virtual machines running on ESX servers while moving it — virtual machines can now be kept running even while they migrate to different hosts. VMware has two main products for the data center, VMware ESX and VMware GSX. Currently VMware is running a beta program for the successor of GSX called VMware Server. VMware ESX server is considered to be their flagship product for running enterprise applications in the datacenter. ESX allows for a 60 to 80% increase in x86 utilization since it is loaded on at the bare metal. VMware GSX and now their beta product VMware Server are both considered data center applications, but rely on a base operating system to be loaded on. As such there is additional overhead when running these two products. The advantage that GSX, and Server, have over ESX is the support for a wider array of devices such as USB connectivity and certain PCI devices. IMPLEMENTATION Conventional emulators like Bochs emulate the Microprocessor , executing each guest CPU instruction by calling a software subroutine on the host machine that simulates the function of that CPU instruction. This abstraction allows the guest machine to run on host machines with a different type of microprocessor, but is also very slow. An improvement on this approach is Dynamically Recompiling blocks of machine instructions the first time they are executed, and later using the translated code directly when the code runs a second time. This approach is taken by Microsoft 's Virtual PC for Mac OS X . VMware Workstation takes an even more optimized approach and uses the CPU to run code directly when this is possible. This is the case for user mode and Virtual 8086 Mode code on x86. When direct execution is not possible, code is rewritten dynamically. This is the case for kernel-level and Real Mode code. In VMware's case, the translated code is put into a spare area of memory, typically at the end of the address space, which can then be protected and made invisible using the segmentation mechanisms. For these reasons, VMware is dramatically faster than emulators, running at more than 80% of the speed that the virtual guest OS would run on hardware. VMware boasts an overhead as small as 3%-6% for computationally intensive applications. Although VMware virtual machines run in user mode, VMware Workstation itself requires installing various drivers in the host operating system, notably in order to dynamically switch the GDT and the IDT tables. One final note: it is often erroneously believed that virtualization products like VMware or Virtual PC ''replace offending instructions'' or ''simply run kernel code in user mode''. Neither of these approaches can work on x86. Replacing instructions means that if the code reads itself it will be surprised not to find the expected content; it is not possible to protect code against reading and at the same time allow normal execution; replacing in place is complicated. Running the code unmodified in user mode is not possible either, as most instructions which just read the machine state do not cause an exception and will betray the real state of the program, and certain instructions silently change behavior in user mode. A rewrite is always necessary; a simulation of the current Program Counter in the original location is performed when necessary and notably hardware code Breakpoint s are remapped. FEATURES Besides bridging to network adapters, CD-ROM readers, hard disk drives, and USB devices, VMware Workstation also provides the ability to simulate some hardware. For example, an ISO file can be mounted as a CDROM, .vmdk files can be mounted as hard disks, and the network adapter driver can be configured to use network address translation through the host machine rather than bridging through it (which would require an IP address for each guest OS on the host network). VMware Workstation also allows LiveCD s to be tested without first Burning them onto physical discs or Reboot ing the computer. You can also take snapshots of an OS running under VMware Workstation. Each snapshot allows you to roll back the virtual machine to the saved status at any time. The Multiple snapshots feature makes VMware Workstation very popular as a tool for sales people to demonstrate complex software products, and for developers to create virtual development and test environments. VMware Workstation includes the ability to designate multiple virtual machines as a team, which can then be powered on and off, suspended and resumed as one object—making it particularly useful for testing client-server environments. New enterprise-grade servers and tools from VMware, Inc. are making it popular to migrate older production servers into virtual machines so that many legacy servers can be consolidated onto a single new host machine with little effort. ISSUES Older versions of VMware seem unable to run newer versions of Linux (kernel 2.4 series seem to panic when run on VMware 2.x, and 2.6 series kernels, when run on VMware 3.x, give a protection error). However, VMware Workstation is now up to version 5.5.1 which supports these newer operating systems and kernels. However, for the latest version(s) of the 2.6.x kernel, a patch is required to use all the VMware features—even when using VMware Workstation 5.0 or 5.5. This patch is freely available as vmware-any-any-updatexxx (at this time it is update101). You can find this patch at http://ftp.cvut.cz/vmware/ Additionally, when using VMware Workstation in an environment where Media Access Control (MAC) addresses are used as unique identifiers (UID), it is advisable (and often required) to manually configure the MAC address for each virtual machine to ensure each is actually unique. One example of such an environment is one in which MAC security is enabled on switches and another example is an environment in which Altiris products are used (if configured to use the MAC address as the UID). If one finds oneself in such a situation, simply disable all networks/adapters other than bridged and edit each virtual machine's .vmx file to change "ethernet0.address" to a unique MAC and "ethernet0.addresstype" to "static". Make sure to also remove the "ethernet0.generatedaddress" entry entirely. SEE ALSO
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