Virtual Server features

Virtual Server features

This topic describes the main features of Virtual Server 2005. Click a heading to show or hide the contents.


Virtual Server provides the following security features:

  • Secure access to administration tools. For access to the Administration Website and the Virtual Machine Remote Control (VMRC) client, Virtual Server supports Secure Sockets Layer (SSL) security, as well as NTLM and Kerberos V5 authentication. For more information, see Configuring Virtual Server security settings.
  • Secure access to configuration and resource files. Each configuration and resource file of Virtual Server is secured by means of file system discretionary access control lists (DACLs). By default, these DACLs restrict access to the file owner and local administrators. For all configuration file types (Virtual Server, virtual machine, and virtual network) and all resource file types (virtual hard disk, virtual floppy disk, undo disk, image, and saved state), you can add and remove user accounts and change permission settings from within the file system. For the Virtual Server configuration file, you can also change security settings from the Administration Website. For more information, see File system security settings for Virtual Server.
  • Configurable user context for virtual machines. By default, a virtual machine runs under the account of the user who turned it on. For added security, you can configure each virtual machine to run under a specified user account. Virtual machine scripts also run under this account, and it must be configured before virtual machine scripts can run. For more information, see Modifying general virtual machine properties.

For background information about Virtual Server security, see Security Considerations for Virtual Server. For more information about configuring Virtual Server security, see Securing Virtual Server.


Virtual Server provides the following management features:

  • Administration Website. The Administration Website is a browser-based tool for configuring and managing Virtual Server and its associated virtual machines and virtual networks. For more information, see Using the Administration Website.
  • Virtual Machine Remote Control. Virtual Machine Remote Control (VMRC) allows you to remotely manage virtual machines running on Virtual Server. From the Virtual Server Administration Website, you can select the Remote Control option for a virtual machine, or you can install the Virtual Machine Remote Control client on a separate computer. For more information, see Using the VMRC client to access virtual machines.
  • Scripting API. Virtual Server provides powerful management automation and extensibility through either scripted or programmatic controls. For more information, see "Scripting" later in this topic.
  • Microsoft Windows Management Instrumentation (WMI). Virtual Server provides WMI counters to the host operating system, which can be integrated into a non-Microsoft management solution or passed to Microsoft Operations Manager for monitoring and alerting. For more information, see Virtual Server WMI class.
  • System event log. Virtual Server logs events on the host operating system event log, which can be integrated into a non-Microsoft management solution, or passed to Microsoft Operations Manager for alerting. Virtual Server can send event notices—such as when a virtual machine session has stopped functioning—to external scripts. In addition, the Administration Website allows you to specify command-line actions to take when certain events occur. For more information, see Configuring Virtual Server scripts.
  • Interoperability with Windows Server System management products. You can manage Virtual Server by using tools such as Automated Deployment Services, Windows Software System Update Services, System Management Services, and Microsoft Operations Manager. For more information, see Virtual Server tools.

For management tasks, Virtual Server uses the following industry-standard technologies:

  • Hypertext Transfer Protocol (HTTP). Virtual Server monitoring and configuration is performed by using the Administration Website, which uses HTTP and a Web interface, so that you can administer Virtual Server and virtual machines by using Microsoft Internet Explorer 5.5 or later. For more information, see Using the Administration Website.
  • Remote Desktop Protocol (RDP). For remote administration of Virtual Server and virtual machines, you can use Remote Desktop Connection.
  • Extensible Markup Language (XML). Virtual Server, virtual machine, and virtual network configuration information is stored in XML-based files. The XML file format enables configuration management from external management software for tasks such as asset management, automated provisioning, and automated deployment. For more information about the configuration files in Virtual Server, see Virtual Server configuration file entries.

Virtual machine infrastructure

Virtual Server provides the software infrastructure to create and manage virtual machines and to interact with guest operating systems. Virtual Server can support up to a maximum of 64 virtual machines. The practical limit of how many virtual machines you can run simultaneously depends on system resources, the amount of memory assigned to each virtual machine, and the total memory available on the physical computer. Virtual Server also supports up to 3.6 gigabytes (GB) of RAM per virtual machine. For more information, see System requirements for Virtual Server.

Virtual Server encapsulates each virtual machine and its installed operating system and applications in a virtual hard disk (.vhd) file that can be easily relocated to a different computer running Virtual Server. It also manages the resources used by virtual machines, and isolates each virtual machine so that it cannot access and use resources of other virtual machines or the host operating system.

For more information about virtual machines, see Virtual machines in Virtual Server. For more information about Virtual Server and virtual machine architecture, see Architecture.


Virtual networks connect virtual machines to internal or external networks. You can configure up to four virtual network connections for each virtual machine. You can also configure an unlimited number of virtual networks. Virtual Server setup creates one internal virtual network to enable networking between virtual machines, as well as one virtual network for each physical Ethernet network adapter to connect virtual machines to external networks. Each virtual network is implemented in a separate virtual network configuration (.vnc) file for access control.

Virtual Server supports only Ethernet network topologies.

For more information, see Virtual networks and Virtual network architecture.

Data storage

The data for each virtual machine is stored in one or more virtual hard disk (.vhd) files. For each virtual machine, you configure a virtual IDE or SCSI device, and Virtual Server maps this to a virtual hard disk file. Virtual machines can access .vhd files on any storage topology supported by the underlying host operating system, including storage area network (SAN) configurations. Virtual hard disks can be configured in several different formats. For more information, see Virtual hard disks.

CPU and memory configuration

Virtual Server supports flexible memory configuration and dynamic CPU resource allocation for each virtual machine, as follows:

  • Memory configuration. Virtual Server allows you to configure memory separately for each virtual machine. You can allocate up to 3.6 gigabytes (GB) of RAM to each virtual machine, depending on the amount of RAM available on the physical computer. Memory overcommit (page sharing) is not supported because of performance and reliability considerations. For more information, see Allocating system resources to a virtual machine.
  • CPU resource allocation. Virtual Server supports both weight-based and constraint-based CPU resource allocation for balanced workload management.

For more information, see Configuring CPU resources for virtual machines.


Virtual Server provides a full-featured Component Object Model (COM) scripting model so that you can use scripts to control every aspect of Virtual Server functionality. Because the scripting model is based on COM technology, you are not limited to using a specific scripting language, but can choose among development languages such as Microsoft Visual Basic® .NET, C, C++, and C#. Furthermore, you can configure scripts to run when certain events occur within Virtual Server. This extensive scripting support provides ease of customization and automation. For more information, see Virtual Server scripting support.


Virtual Server provides simple two-node failover from one virtual machine to another for testing and development. Both nodes must be on the same physical hardware, and the shared cluster volume must be a fixed-size virtual hard disk; you cannot use dynamically expanding virtual hard disks. For more information about implementing clusters, see Clustering virtual machines.

Because server clustering with Virtual Server is limited to simple failover from one virtual machine to another on the same physical computer, this solution does not mitigate a failure of the physical computer hardware. For this reason, Microsoft supports clustering with Virtual Server only in a test or development environment.