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Server availability

Updated: January 21, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Server availability

This topic contains a brief overview of the features that support server availability. It is divided into two sections: New and updated features since Windows NT 4.0 and New and updated features since Windows 2000.

For links to more information about the features in this release, see New Features.

Availability is a level of service provided by applications, services, or systems. Highly available systems have minimal downtime, whether planned or unplanned. The Windows Server 2003 family supports high levels of server availability for your critical business solutions. This operating system also gives you clustering, advanced fault tolerance, and file system recoverability features.

New and updated features since Windows NT 4.0

The Windows Server 2003 family offers the following improvements (in comparison to Windows NT) that help provide increased levels of server availability:

Server clusters (Windows Server 2003, Enterprise Edition and Windows Server 2003, Datacenter Edition only)
Server clusters provide high availability, scalability, and manageability for important resources and applications. Multiple servers (nodes) in a cluster remain in constant communication. If one of the nodes in a cluster is unavailable as a result of failure or maintenance, another node immediately begins providing service (a process known as failover). Users who access the cluster are constantly connected to server-based resources. For more information, see Windows Clustering.

Network Load Balancing
Network Load Balancing enhances the availability and scalability of Internet server programs on mission-critical servers. The two principal functions of Network Load Balancing are to provide high availability for Web server programs and to scale server performance. By combining the resources of two or more computers into a single cluster, Network Load Balancing delivers reliability and performance by distributing the incoming network traffic. For more information, see Network Load Balancing Overview.

Fewer server restarts
Configuring hardware and software is easier, because you can perform many activities without restarting the server. These activities include, but are not limited to:

  • Extending a storage volume

  • Configuring network protocols

  • Managing storage dynamically (Dynamic Volume Management)

  • Reconfiguring settings on Peripheral Component Interconnect (PCI) and other Plug and Play hardware

Plug and Play
With Plug and Play, a combination of hardware and software support, the server can recognize and adapt to hardware configuration changes automatically, without your intervention and without restarting. With Plug and Play, planned system restarts are reduced by more than 90 percent.

Start from mirrored volumes
With appropriate preparation, you can start your server from a redundant copy of data on a mirrored volume, which increases system availability during server recovery or planned maintenance. For more information, see Using mirrored volumes.

New and updated features since Windows 2000

The Windows Server 2003 family offers the following improvements (in comparison to Windows 2000) that help provide increased levels of server availability:

User State Migration Tool
The User State Migration Tool (USMT) aids deployment by capturing and restoring user settings, files, and documents. Users do not have to reconfigure desktop settings for such things as e-mail servers, proxy servers, desktop color schemes, and desktop wallpaper.

Emergency Management Services
With Emergency Management Services, combined with the appropriate hardware, you can perform remote management and system recovery tasks, even when the server is not available through the standard remote administration tools and mechanisms. For more information, see Emergency Management Services.

Storage area network and network-attached storage support
Storage area network (SAN) and network-attached storage (NAS) support in the Windows Server 2003 family has a number of new system enhancements to increase server availability. These improvements include fault tolerant, network-attached scenarios, such as connecting to SAN and NAS servers. When connecting to SANs, the Windows Server 2003 family supports multipath failover, which enables redundant paths from the host server (running Windows 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server, or any product in the Windows Server 2003 family) to the SAN volume. The Windows Server 2003 family also supports connecting to NAS and being used as a NAS.

Network Load Balancing enhancements
Several improvements have been made to Network Load Balancing in this release:

  • Network Load Balancing can now be bound to multiple network adapters, so that you can configure multiple independent clusters on each host. For more information about virtual clusters, see Virtual clusters.

  • Network Load Balancing uses Internet Group Management Protocol (IGMP) support for limiting switch flooding, so that traffic intended for a Network Load Balancing cluster passes through only those ports that serve the cluster hosts and not through all switch ports.

  • With Network Load Balancing Manager, you can create new Network Load Balancing clusters, and you can configure and manage clusters and all the cluster's hosts from a single remote or local computer.

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