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Introducing Windows 2000 Clustering Technologies
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Posted: Thursday, February 17, 2000
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Microsoft® Windows® 2000 Advanced Server and Datacenter Server operating systems enable organizations to deploy business-critical e-commerce and line-of-business applications on industry-standard computer hardware. Clustering technologies are key tools in making this possible.
Clustering refers to linking individual servers physically and programmatically and coordinating communication between them so they can perform common tasks. Should any one server stop functioning, a process called failover automatically shifts its workload to another server to provide continuous service. In addition to failover, some forms of clustering also employ load balancing, which enables the computational workload to be distributed across a network of linked computers.
Combined with advanced symmetric multiprocessing (SMP) and large memory support in both Windows 2000 Advanced Server and Datacenter Server operating systems, Windows clustering technologies enable organizations to ensure the availability of critical applications while being able to scale those applications both up and out to meet increased demand.
Defining a Cluster in Windows 2000
A cluster is a group of independent computers that work together to run a common set of applications and provide the image of a single system to the client and application. The computers are physically connected by cables and programmatically connected by cluster software. These connections allow computers to use failover and load balancing, which is not possible with a stand-alone computer.
Windows 2000 clustering technology provides high availability, scalability, and manageability:
 | High availability. The cluster is designed to avoid a single point-of-failure. Applications can be distributed over more than one computer, achieving a degree of parallelism and failure recovery, and providing more availability. |
| Scalability. You can increase the cluster's computing power by adding more processors or computers. |
| Manageability. The cluster appears as a single-system image to end users, applications, and the network, while providing a single point-of-control to administrators. This single point-of-control can be remote. |
Two Types of Clusters in Windows 2000
In the Windows 2000 Advanced Server and Datacenter Server operating systems, Microsoft introduces two clustering technologies that can be used independently or in combination, providing organizations with a complete set of clustered solutions that can be selected based on the requirements of a given application or service. Windows clustering technologies are illustrated in figure 1 and include:
| Cluster service. This service is intended primarily to provide failover support for applications such as databases, messaging systems, and file and print services. Cluster service supports 2-node failover clusters in Windows 2000 Advanced Server and 4-node clusters in Datacenter Server. Cluster service is ideal for ensuring the availability of critical line-of-business and other back-end systems, such as Microsoft Exchange Server or a Microsoft SQL ServerTM 7.0 database acting as a data store for an e-commerce Web site. |
| Network Load Balancing (NLB). This service load balances incoming Internet Protocol (IP) traffic across clusters of up to 32 nodes. Network Load Balancing enhances both the availability and scalability of Internet server-based programs such as Web servers, streaming media servers, and Terminal Services. By acting as the load balancing infrastructure and providing control information to management applications built on top of Windows Management Instrumentation (WMI), Network Load Balancing can seamlessly integrate into existing Web server farm infrastructures. Network Load Balancing will also serve as an ideal load balancing architecture for use with the Microsoft release of the upcoming AppCenter Server in distributed Web farm environments. |
Figure 1. Both Windows clustering technologies deployed in a typical e-commerce environment.
The Value of Cluster Service
Line-of-business applications are applications that are central to a company’s operations, and include systems such as databases, messaging servers, enterprise resource planning (ERP) applications, and core file and print services. Cluster service in the Windows 2000 operating system ensures that these critical applications are online when needed by removing the physical server as a single point-of-failure.
In the event that a hardware or software failure occurs in either node, the applications currently running on that node (and you may run more than one), are then migrated by Cluster service to the surviving node and re-started. Because Cluster service uses a shared-disk configuration with common bus architectures such as SCSI and Fibre Channel, no data is lost during a fail-over.
The benefits of deploying the Windows 2000 operating system with Cluster service are:
| Reduce unplanned downtime: Downtime caused by hardware or software failures can result in lost revenue, wasted IT staff work, and unhappy customers. Using Cluster service with a shared-disk solution on critical line-of-business applications can significantly reduce the amount of application downtime caused by unexpected failures. |
| Smoothly deploy upgrades with rolling upgrade support: Cluster service is ideally suited for ensuring transparent upgrades of applications without interrupting your clients. By migrating your applications to one node, upgrading the first node, and then migrating them back, you can roll out hardware, software, and even operating systems upgrades without taking the application offline. Cluster service in Windows 2000 supports rolling operating system upgrades from Windows NT® Server 4.0, Enterprise Edition clusters deployed with Service Pack 4 or higher. |
| Deploy the applications you rely on: Cluster service is supported by dozens of cluster-aware applications spanning a wide range of functions and vendors. Cluster-aware applications include databases such as Microsoft SQL Server 7.0 and IBM DB2, messaging servers such as Microsoft Exchange Server 5.5 and Lotus Domino, management tools like NetIQ’s AppManager, disaster recovery tools like NSI Software’s DoubleTake 3.0, and ERP applications including SAP, Baan, PeopleSoft, and JD Edwards. And you can now cluster such services as DHCP, WINS, SMTP, and NNTP. |
| Deploy the applications on which you rely on industry-standard hardware: Keep costs down by deploying Cluster service clusters on standard computer server and storage hardware, avoiding costly and often proprietary alternative high-availability solutions. Cluster service solutions are currently offered by most systems vendors including Dell, Compaq, IBM, Hewlett-Packard, Unisys, and Data General. |
Finally, Cluster service in Windows 2000 is now easier to set up and use than ever before. With a substantially improved Setup wizard, Cluster service setup requires less entries and less time to install and configure than with Windows NT Server 4.0, Enterprise Edition. Combined with the improved Cluster Administrator (now a Microsoft Management Console snap-in), the Cluster service in the Windows 2000 operating system is redefining how simple building clusters on standard Intel PC-based hardware can be.
The Value of Network Load Balancing
With the explosive growth of the Internet and associated services (intranets, extranets, and hosted applications), the need for dynamic scalability of Web servers has never been greater. With Network Load Balancing (NLB), Windows 2000 provides an integrated infrastructure for building your critical, in-demand Web sites in a distributed, load-balanced manner. Combined with the distributed application features of Component Services and the enhanced scalability of Internet Information Services (IIS) 5.0, NLB helps ensure that your Web services can scale to handle the heaviest of traffic loads, while also guarding against both planned and unplanned server downtime.
The benefits of deploying Network Load Balancing are:
| Scale Web applications by quickly and incrementally adding additional servers: Plan for the future by deploying an NLB cluster one server at a time, while avoiding substantial up-front costs for expensive proprietary hardware-based load balancing systems. Designed for use with a diverse array of applications and services, Network Load Balancing uses a statistical load-balancing model to distribute incoming IP requests across a cluster of up to 32 servers. Because it is integrated into the Windows 2000 networking infrastructure, NLB is a simple, effective means of adding capacity to Windows 2000-based, Web-based applications. |
| Ensure that your Web sites are always online for your customers: With sub-10 second failover time for Web servers clustered with NLB, your customers’ buying or browsing experience will never be interrupted by either planned upgrades or maintenance, or unplanned server downtimes. Combined with application health monitoring tools such as the Microsoft ClusterSentinel, which is included in the Windows 2000 Resource Kit, NLB is the quick, no-hassle means of making sure your site is online when your customers need it. |
| Build for Microsoft AppCenter Server tomorrow: Deploying your site today using the NLB service in the Windows 2000 operating system ensures that your site is ready for deploying Microsoft AppCenter Server tomorrow. AppCenter Server includes management, monitoring, and replication features that are ideal complements for Web server clusters built with NLB. AppCenter Server will also include advanced setup and management features specifically tailored to enhance NLB clusters. |
Network Load Balancing in Windows 2000 Advanced Server and Datacenter Server, and its predecessor in Windows NT Server 4.0, Enterprise Edition, are in use on some of the world’s most popular Web destinations, including Microsoft Web properties (Microsoft.com, MSNTM, MSNBC, Expedia®), Dell.com, and TV Guide Online.
Using the Two Together
Both Windows Clustering technologies can be used in conjunction to create highly scalable and available n-tier e-commerce sites. By deploying Network Load Balancing across a front-end Web server farm, and clustering back-end line-of-business applications such as databases with Cluster service, you can gain all the benefits of near-linear scalability with no server or application-based single points-of-failure. Combined with industry-standard best practices for designing high-availability networking infrastructures, you can ensure your Windows 2000-based Internet-enabled business will be online all the time and can quickly scale to meet demand.
For More Information
Sources of additional information on the Windows clustering technologies can be found on the Microsoft Web sites:
General Information About Microsoft Clustering Technologies
Microsoft Windows 2000 Advanced Server
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Last Updated: Wednesday, February 16, 2000
© 2000 Microsoft Corporation. All rights reserved. Terms of use.
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