One of the major advantages of mainframe operating systems such as IBM's MVS (Multiple Virtual System) and VM (Virtual Machine) is the ability to create a virtual machine--a self-contained environment in which a guest OS runs on top of a host OS. Each virtual machine can host an independent operating system, isolated from any others; any problems or crashes in one VM will not bring down another. With IBM mainframes running MVS/VM, the ability to run virtual machines on a single mainframe eliminates the need to have multiple multimillion-dollar mainframes for separate production and test systems. With VMware GSX Server, companies can reap the benefits provided by mainframe virtual machines on standard PCs running Linux.
Features
GSX Server supports a maximum of four virtual machines per processor; it also supports multiprocessor systems with up to eight processors. Theoretically, it's possible to run as many as 32 virtual machines simultaneously. As you'd expect, the product has some hefty system requirements: a minimum of 256MB of RAM, at least a 400MHz CPU, and, because each VM requires a complete OS installation, a significant amount of disk space. GSX Server itself consumes only about 30MB, depending on the options installed. For guest operating systems, GSX Server supports most flavors of Linux, in addition to Microsoft products ranging from MS-DOS 6.0 to Windows 2000.
Installation
We tested GSX Server on two systems: a 400MHz Dell OptiPlex with 256MB of RAM and a Dell PowerEdge 1GHz server with 512MB of RAM--both running Red Hat 7. After downloading 20MB of RPM packages for the GSX Server console and the Windows-based console and Web administration tool, installation required nothing more than an rpm -i command.
Configuring the product requires a little more effort. To set configuration parameters, you must run a Perl script that prompts for the required information; fortunately, the default choices are usually the most appropriate. Once this process is complete, you must run a virtual machine creation wizard to create a configuration file for each guest operating system. Also, you may need to tweak the configuration files for the host operating system so that devices can be detected properly by the guest OS.
Testing
To test GSX Server, we installed three guest operating systems: Windows 98 SE, Windows 2000, and Red Hat 7. The installation process for each guest OS is virtually identical to each one's regular installation process. For instance, to install Windows 98, we inserted a Windows 98 boot floppy into our system's floppy drive and put the Windows 98 CD into the CD-ROM drive. Once it powered up, the virtual system booted to the floppy, and the installation process proceeded normally. The Windows 2000 installation process suffered from excruciatingly slow probing for hardware but was otherwise typical. Installing a Linux guest operating system, on the other hand, was simple and quick and caused no hardware detection problems.
Once a guest OS installation is complete, you can use the GSX Server console to boot and interact with each operating system remotely. The console is an X application window that displays the output of a virtual machine's OS, allowing you to boot and interact with each guest OS from any remote system on your network. Since each OS can be configured with different virtual network settings, you can run two separate Web servers on one machine, for example, one under the Red Hat guest OS and another under Windows 2000.
Hefty hardware needed
With such flexibility, it's not surprising that GSX Server is a resource hog. When we launched our Windows 2000 guest OS, performance on our 400MHz OptiPlex with 256MB of RAM slowed to a standstill. Our PowerEdge box fared much better; with twice the amount of RAM and the 1GHz CPU, there was a noticeable improvement in responsiveness.
Bottom line
VMware GSX Server is an enterprise-level product and is priced accordingly. The electronic distribution, which can be downloaded from VMware's Web site, costs $2,499, and a packaged version including documentation costs about $50 more. VMware's Workstation product, designed for individual users, is available for $299 and offers much of the same functionality. Considering its tremendous power and flexibility, VMware GSX Server is an absolute must for any company looking to maintain multiple centralized development environments.
