Put many operating systems under one roof

An emulator translates machine instructions into other instructions. For instance, you could be emulating a SPARC instruction working on an Intel machine. There is software that emulates all the Windows calls, so that Windows applications can run on Linux.

If you virtualize an architecture and directly execute the instruction, you can achieve a higher level of performance and have multiple virtual machines running simultaneously. Once you have a virtual machine you can run any operating system you want on it. That gives you more flexibility and at less cost.

The advantage of machine virtualization over machine emulation is that you get better performance. You also get completeness. You don't have to keep up with the operating system APIs. All you have to do is virtualize the finite machine instruction set and you're done. Someone emulating operating system calls will have to deal with a large number of APIs in an operating system. Unlike a hardware architecture, the operating system and its APIs are constantly changing, like a moving target.

Actually, Windows on Windows is the biggest market for us. Most of our customers want to run multiple Windows operating systems. There are people who use VMware to get Windows applications running on Linux, too.

The big benefit to having multiple operating systems running at the same time on a server is that you can logically partition that server into very isolated, complete machine environments. Then, the applications running in different virtual machines could crash independently, have different security paradigms, and so on. Virtualization leverages the resources of the hardware and creates more efficiency.

Virtualization also removes a lot of constraints. Once you build a virtual machine environment with an OS and an application, it's a completely encapsulated environment. You could move that environment to another machine, and it would run just the same as it was running on the previous machine. What people find is that they can do a lot of server consolidation in a test-dev lab. Each developer could have their own virtual server without having another physical server.

Virtualization is right for any business that wants to put many applications on one machine. Virtualization is appropriate for those who want to eliminate incompatibilities between applications or operating systems. It provides tremendous efficiencies in the provisioning and deployment of services due to the fact that the service can be built once and then customized as required for each customer's deployment.

Virtualized storage creates one big storage entity, ridding users and managers of concerns about the details of this disk or that controller. It's completely parallel to virtual computing, which creates one big computing entity and hides the complexity of the hardware or OS that is running.

In virtual computing, you've created a layer that can run on all the machines. The entities are the applications that are just services that run anywhere. In storage virtualization, you have data that can be located anywhere on a virtualized storage layer. In virtual computing, your services can run anywhere on this virtualized computing layer.

This is a tremendous boon to management. When you have a virtualization abstraction, for example, it's possible to create high availability and fault tolerance more cost effectively. The virtualization layer can span all the physical machines. You can clone that virtual machine and have the copy sitting on another physical machine. If one machine goes down, the virtual machine continues to run. You can hide all this through a management interface and think of it as managing one centralized entity.

The centralized management boosts productivity tremendously. For example, one VMware customer provisions data collection for oil wells. After implementing virtualization, the deployment process went from two days to a couple of hours.

If you have a huge monolithic application -- such as a giant database -- that uses an entire machine, there's no advantage to adding virtualization software.

Yes. The virtualization layer insulates the user from the hardware, so it's easy to move from one physical machine to an upgraded physical machine or to move software from one machine to another. With the OS, if you have something working in an existing OS and a new OS comes out you can run both of them side by side simultaneously, thus easily maintaining a legacy application. Our new desktop product supports Windows XP and it's a good way for people to try that without wiping out their previous OS along with its applications.

A VMware IT manager working at home installed and implemented a Siebel Systems application on VMware Workstation on his laptop. Then he took that virtual machine and moved it to one of our big servers in the office. He didn't have to change anything. This was a major change in hardware, but all he had to do was move a very large file that was a virtual machine.