Windows IT professionals have recently discovered the benefits of virtual machine (VM) software, a technology that the mainframe world has used for almost two decades. Today's PCs have the processing power required to run VM software, which lets you configure one computer to run multiple OSs.
Companies can use VM software to adopt new OSs (e.g., Windows XP) while continuing to run vital legacy applications that rely on earlier OSs (e.g., DOS, Windows 9x) on the same hardware. Another use for VM software is to create test deployment environments. In the past, creating a test environment might have required IT to dedicate a small fleet of PCs on an isolated LAN for application testing. That LAN might use a couple of test servers for domain controllers (DCs) and additional systems for each OS used in the organization. VM software lets you consolidate most of your testing systems onto one or two physical systems that run guest VMs for each test platform.
VM software is also useful for IT support departments. IT support staff often must recreate customer deployment scenarios to solve problems. VM software makes it much easier to quickly reproduce a given customer scenario. Furthermore, you can set up a VM product to automatically discard your unique configuration changes when you're finished with a particular deployment scenario, letting you resume customer support from a clean slate. This feature also makes VM software useful for setting up training scenarios in which you always want the system to start from a predefined state.
VMware and Microsoft offer desktop VM products for Windows. VMware Workstation 4 and Microsoft Virtual PC 2004 are similar in overall functionality but have some important differences. To evaluate their features and see which product might work best for your environment, you can use this review and the features comparison in Table 1.
Product Evaluation Criteria
An important criterion for evaluating VM products is the products' support for host and guest OSs. The host OS is the OS platform on which you install the VM software. The guest OSs are the OSs that the products support as VMs. Here, more is better: The more host and guest OSs the VM product supports, the more flexibility you have for installing the VM software and setting up test scenarios. Figure 1 shows the relationship between the VM software and host and guest OSs.
Another key evaluation factor is how the VM software addresses the physical hardware available on the host system and provides virtual hardware for the guest VMs. Access to RAM is a vital factor and is usually the gating factor for supporting a number of active VMs. The more RAM the VM software can address, the more VMs can be active at a given time. Another important host hardware characteristic is the ability to access real disk partitions and share disk partitions between VMs. The ability to access real disk partitions can provide a performance advantage over pure virtual disks and can let a VM access multiboot partitions. Additionally, the ability to access real disk partitions can let you make your VMs portable by building them on DVD media.
Some key considerations for the guest OS are the product's support for enhanced graphics and sound in the guest OS and support for CD-ROM and USB devices. Other useful features include support for changing VM settings such as name, maximum RAM available to the VM, and maximum hard disk space. Another important factor is the ability to move VMs between host platforms, which can make your testing environment more flexible and help you deploy VMs more easily.
VMware Workstation 4
VMware Workstation 4, which VMware released in April 2003, actually is the fourth release of the company's VMware Workstation product (bucking the trend of fictitious version numbers). The first VMware Workstation version, released in 1999, was the first x86 processor-based VM product. VMware, a subsidiary of EMC, also makes two server-based VM products: VMware GSX Server and VMware ESX Server. For more information about the VMware server products, see the sidebar "VM Server Products."
VMware Workstation 4 provides flexible support for host and guest OSs. Host support is undoubtedly the biggest difference between VMware Workstation and Virtual PC. Virtual PC officially supports only two Microsoft OSs; VMware Workstation supports many OSs and can run most x86 OSs. Among the OSs VMware Workstation supports are Windows Server 2003 (Standard, Enterprise, and Web editions); Windows XP Professional and Home Editions with Service Pack 1 (SP1); Windows 2000 Advanced Server and Professional; Windows NT Server 4.0 with SP6a, and NT Workstation 4.0. VMware Workstation also extends beyond Microsoft OSs, supporting several popular Linux distributions, including MandrakeSoft's Mandrake Linux 8.2 (and later); Red Hat Linux Advanced Server 2.1 (and later) and Red Hat Linux 7.0 (and later); and SuSE Linux Enterprise Server 7 (and later) and SuSE Linux 7.3 (and later). The Windows and Linux hosts are on the same VMware Workstation installation disk.
I installed and tested VMware Workstation on a 1.8GHz system with 1GB of RAM. The product's installation was easy and uneventful and took about 1 minute. After VMware Workstation is installed, you manage it by using the VMware Workstation window, which Figure 2 shows. I found the VMware Workstation window to be an intuitive, useful management console, with only one minor inconvenience: I couldn't resize the window. However, the window automatically resized when I changed the guest OS's resolution.