What is VMWare?
Overview of VMWare Virtual Machine
VMware, Inc. is a subsidiary of Dell Technologies that provides cloud and virtualization software and services  and claims to be the first to successfully virtualize the x86 architecture commercially. Founded in 1998, VMware is based in Palo Alto, California. In 2004, it was acquired by and became a subsidiary of EMC Corporation, then on August 14, 2007, EMC sold 15% of the company in a New York Stock Exchange IPO. The company trades under the symbol VMW.
VMware’s desktop software runs on Microsoft Windows, Linux, and macOS, while its enterprise software hypervisors for servers, VMware ESX and VMware ESXi, are bare-metal hypervisors that run directly on server hardware without requiring an additional underlying operating system.
In anticipation of Dell’s acquisition of parent company EMC, VMware announced a restructuring in January 2016 to reduce about 800 positions, and some executives resigned. There were doubts about the company’s future and its product lines, particularly for the desktop. In August 2016, announcing the release of new desktop products, the company said “we’re very much alive and well”.
In 1998, VMware was founded by Diane Greene, Mendel Rosenblum, Scott Devine, Ellen Wang and Edouard Bugnion. Greene and Rosenblum, who are married, first met while at the University of California, Berkeley. Edouard Bugnion remained the chief architect and CTO of VMware until 2005, and went on to found Nuova Systems (now part of Cisco). For the first year, VMware operated in stealth mode, with roughly 20 employees by the end of 1998. The company was launched officially early in the second year, in February 1999, at the DEMO Conference organized by Chris Shipley. The first product, VMware Workstation, was delivered in May 1999, and the company entered the server market in 2001 with VMware GSX Server (hosted) and VMware ESX Server (hostless).
In 2003, VMware launched VMware Virtual Center, the VMotion, and Virtual SMP technology. 64-bit support appeared in 2004. The same year, the company was acquired by EMC Corporation for US$625 million.
In August 2007, EMC released 15% of the company’s shares in VMware in an initial public offering on the New York Stock Exchange. The stock debuted at US$29 per share and closed the day at US$51.
On July 8, 2008, VMware co-founder, president and CEO Diane Greene, was unexpectedly fired by the VMware Board of Directors and replaced by Paul Maritz, a retired 14-year Microsoft veteran who was heading EMC’s cloud computing business unit. In the same news release VMware stated that 2008 revenue growth will be “modestly below the previous guidance of 50% growth over 2007”. As a result, market price of VMware dropped nearly 25%. Then, on September 10, 2008, Rosenblum, the company’s chief scientist, resigned.
On September 16, 2008, VMware announced a collaboration with Cisco Systems. One result was the Cisco Nexus 1000V, a distributed virtual software switch, an integrated option in the VMware infrastructure.
On April 12, 2011, VMware released an open source platform-as-a-service system called Cloud Foundry, as well as a hosted version of the service. This supported application deployment for Java, Ruby on Rails, Sinatra, Node.js, and Scala, as well as database support for MySQL, MongoDB, Redis, Postgres, RabbitMQ.
In March 2013, VMware gave details of a spin-off of Pivotal. All of VMware’s application- and developer-oriented products, including Spring, tc Server, Cloud Foundry, RabbitMQ, GemFire, and SQLFire were transferred to this organization. It also announced that it was introducing its own IaaS service, vCloud Hybrid Service, in a shift of its strategy of selling software to cloud service providers.
In April 2013, Pivotal was formally created with GE as a minority shareholder.
In May 2013, VMware launched vCloud Hybrid Service at its new Palo Alto headquarters (vCloud Hybrid Service now known as vCloud Air), announcing an early access program in a Las Vegas data center. The service is designed to function as an extension of its customer’s existing vSphere installations, with full compatibility with existing virtual machines virtualized with VMware software and tightly integrated networking. The service is based on vCloud Director 5.1/vSphere 5.1.
In September 2013 at VMworld San Francisco, VMware announced general availability of vCloud Hybrid Service and expansion to Sterling, Virginia, Santa Clara, California, Dallas, Texas, and a service beta in the UK. It also pre-announced a disaster recovery and desktop-as-a-service offering based on Desktone, which it went on to acquire in October 2013.
Following the news in early 2016 of the impending acquisition by Dell, and despite Dell’s assurance that VMware would remain independent, VMware president and COO Carl Eschenbach left VMware to join Sequoia Capital, and Martin Casado, VMware’s general manager for its Networking and Security business, left for Andreessen Horowitz. Analysts commented that the cultures at Dell and EMC, and at EMC and VMware, are different, and said that they had heard that impending corporate cultural collisions and potentially radical product overlap pruning, would cause many EMC and VMware personnel to leave; VMware CEO Pat Gelsinger, following rumours, categorically denied that he would leave. 
Core product design
VMware developed a range of products, most notable of which are their hypervisors. VMware became well known for their first type 2 hypervisor known as GSX. This product has since evolved into two hypervisor products lines: VMware’s type 1 hypervisors running directly on hardware and their hosted type 2 hypervisors.
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 system 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. Alternatively, 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 (or, with vMotion Storage, separate storage can be used, too). Each of these transitions is completely transparent to any users on the virtual machine at the time it is being migrated.
VMware Workstation, Server, and ESX take a more optimized path to running target operating systems on the host than that of emulators (such as Bochs) which simulate the function of each CPU instruction on the target machine one-by-one, or that of dynamic recompilation which compiles blocks of machine-instructions the first time they execute, and then uses the translated code directly when the code runs subsequently (Microsoft Virtual PC for macOS takes this approach). VMware software does not emulate an instruction set for different hardware not physically present. This significantly boosts performance, but can cause problems when moving virtual machine guests between hardware hosts using different instruction sets (such as found in 64-bit Intel and AMD CPUs), or between hardware hosts with a differing number of CPUs. Software that is CPU agnostic can usually survive such a transition, unless it is agnostic by forking at startup, in which case, the software or the guest OS must be stopped before moving it, then restarted after the move.
VMware’s products predate the virtualization extensions to the x86 instruction set, and do not require virtualization-enabled processors. On newer processors, the hypervisor is now designed to take advantage of the extensions. However, unlike many other hypervisors, VMware still supports older processors. In such cases, it uses the CPU to run code directly whenever possible (as, for example, when running user-mode and virtual 8086 mode code on x86). When direct execution cannot operate, such as with kernel-level and real-mode code, VMware products use binary translation (BT) to re-write the code dynamically. The translated code gets stored in spare memory, typically at the end of the address space, which segmentation mechanisms can protect and make invisible. For these reasons, VMware operates dramatically faster than emulators, running at more than 80% of the speed that the virtual guest operating system would run directly on the same hardware. In one study VMware claims a slowdown over native ranging from 0–6 percent for the VMware ESX Server.
VMware’s approach avoids some of the difficulties of virtualization on x86-based platforms. Virtual machines may deal with offending instructions by replacing them, or by simply running kernel code in user mode. Replacing instructions runs the risk that the code may fail to find the expected content if it reads itself; one cannot protect code against reading while allowing normal execution, and replacing in place becomes complicated. Running the code unmodified in user mode will also fail, 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. One must always rewrite, performing a simulation of the current program counter in the original location when necessary and (notably) remapping hardware code breakpoints.
Although VMware virtual machines run in user mode, VMware Workstation itself requires the installation of various drivers in the host operating system, notably to dynamically switch the Global Descriptor Table (GDT) and the Interrupt Descriptor Table (IDT).
The VMware product line can also run different operating systems on a dual-boot system simultaneously by booting one partition natively while using the other as a guest within VMware Workstation.