Module 2: Concepts of Server Clusters

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Module 2: Concepts of Server Clusters

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  1. Module 2: Concepts of Server Clusters Contents Overview 1 Introduction to Server Clusters 2 Multimedia: Microsoft Windows 2000 Cluster Service 7 Key Concepts of a Server Cluster 9 Demonstration: Cluster Concepts 26 Choosing a Server Cluster Configuration 27 Applications and Services on Server Clusters 36 Review 44
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  3. Module 2: Concepts of Server Clusters iii Instructor Notes Presentation: This module provides students with a brief overview of the different types of 90 Minutes server clusters and their key benefits of availability and scalability. A short video gives an overview of how Cluster service functions, and introduces the Lab: key terms and concepts, which are explained in the Key Concepts of a Server 00 Minutes Cluster section of the module. Students are then introduced to four different cluster configuration options. The last section explains how both cluster-aware and generic services and applications run in a server cluster, including an explanation of how to identify performance limitations, which are caused by these resources. After completing this module, students will be able to: Explain the features of clustering technologies. Define the key terms and concepts of a server cluster. Choose a server cluster configuration. Describe how Cluster service supports applications and services. Materials and Preparation This section provides the materials and preparation tasks that you need to teach this module. Required Materials To teach this module, you need the following materials: Microsoft® PowerPoint® file 2087A_02.ppt Servercluster.avi file on the Instructor CD Preparation Tasks To prepare for this module, you should: Read the materials for this module and anticipate questions students may ask. Preview the servercluster.avi and the review questions and prepare additional questions as necessary. Practice the demonstration. Study the review questions and prepare alternative answers for discussion. Read the Appendix.
  4. iv Module 2: Concepts of Server Clusters Demonstration This section provides demonstration procedures that will not fit in the margin notes or are not appropriate for the student notes. Cluster Concepts To prepare for the demonstration 1. Run the demonstration enough times so you can perform the demonstration without referring to the material. 2. Classroom setup must be complete. 3. The Terminal Services client needs to be installed on the London computer. 4. The Cluster Administrator needs to be installed on the London computer. In this demonstration, you will reinforce the concepts of server clusters and show the students different name resolution capabilities for clients accessing resources from the cluster. Demonstration 1 To start Cluster Administrator from the Run command and view the Cluster Group Owner 1. On the Start menu, click Run. 2. In the Run command dialog box, type Cluadmin.exe -noreconnect 3. Cluster Administrator opens, and in the Open Connection to Cluster dialog box, type MyCluster and then click Open. 4. Show the students the different groups and resources. 5. Point out that the two servers running the cluster are named NodeA and NodeB. 6. Expand Groups, and point out the owner of Cluster Group. Leave Cluster Administrator open. Demonstration 2 To create a public folder share from a Terminal Services session 1. On the Start menu, point to Programs, point to Administrative Tools, and then click Terminal Services Connections. 2. Right-click Terminal Services Connections, and then click Add new connection…. 3. In the Add New Connection dialog box, fill out the following information and then click OK. 4. Server name or IP address: NodeA 5. Connection name: NodeA 6. Perform the previous step and replace NodeA with NodeB. 7. Right-click the Node that is the owner of Cluster Group, and then click Connect. 8. In the Log On to Windows dialog box fill out the following information and click OK.
  5. Module 2: Concepts of Server Clusters v 9. User Name: Administrator@nwtraders.msft 10. Password: password 11. On the desktop, double-click My Computer. 12. In My Computer, double-click drive W: 13. On drive W menu, click File, select New, and then click Folder. 14. Name the folder Public. 15. Close Terminal Services connections MMC. Demonstration 3 To create a File Share resource 1. From Cluster Administrator, expand Groups, and then click Cluster Group. 2. Right-click Cluster Group, select New, and then click Resource. 3. In the New Resource dialog box fill out the following and then click Next. • Name: Public Share • Description: Public Share on MyCluster • Resource type: File Share • Group: Cluster Group 4. In the Possible Owners dialog box, click Next. 5. In the Dependencies dialog box, add the following Resource dependencies, and then click Next. • Cluster Name • Disk W: 6. In the File Share Parameters dialog box fill out the following information and then click Finish. • Share Name: Public • Path: W:\Public • Comment: Public File Share on MyCluster 7. Click OK to confirm that the resource was created successfully. 8. Right-click Public Share, and then click Bring Online. Demonstration 4 To test WINS Name Resolution for the Public Share 1. On the Start menu, click Run. 2. In the Run dialog box, type \\mycluster\public 3. In Microsoft Windows® Explorer, view the contents of the public folder. 4. From Windows Explorer click File, select New, and then click Folder. 5. Name the folder Sales. 6. Close Windows Explorer.
  6. vi Module 2: Concepts of Server Clusters Demonstration 5 To test DNS Name Resolution 1. On the Start menu, click Run. 2. In the Run dialog box, type \\mycluster.nwtraders.msft\public 3. When Windows Explorer opens, view the contents of the public folder. Demonstration 6 To publish a Shared Folder in Microsoft Active Directory™ directory service 1. On the Start menu, point to Programs, then point to Administrative Tools, and then click on Active Directory Users and Computers. 2. On the Tree tab, expand nwtraders.msft. 3. Right-click Users, select New, and then click Shared Folder. 4. In the New Object – Shared Folder dialog box, fill out the following and then click OK. • Name: Public Share on MyCluster • Network path (\\server\share): \\mycluster\public or \\mycluster.nwtraders.msft\public 5. Close Active Directory Users and Computers. 6. On your desktop, double-click My Network Places. 7. In My Network Places, double-click Entire Network. 8. In the Entire Network window, click entire contents on the left side of the screen. 9. In the Entire Network window, double-click Directory. 10. In the Directory window, double-click nwtraders. 11. In the ntds://nwtraders.msft window, double-click Users. 12. In the ntds://nwtraders.msft/Users window, double-click Public. 13. Windows Explorer opens the contents of the public share on mycluster. Demonstration 7 To demonstrate a failover of the Public Share 1. On the Start menu, point to Programs, point to Administrative Tools, and then click Cluster Administrator. 2. If prompted to connect to a cluster, type MyCluster and then click Open. 3. In Cluster Administrator, expand Groups, right-click Cluster Group, and then click Move Group. 4. Show the students how the owner is changing from NodeX to NodeY, X being the original node controlling the Cluster Group and Y being the node that will take control of the Cluster Group.
  7. Module 2: Concepts of Server Clusters vii Demonstration 8 To test WINS Name Resolution after failover 1. On the Start menu, click Run. 2. In the Run dialog box, type \\mycluster\public 3. Windows Explorer opens and you can view the contents of the public folder. Demonstration 9 To test DNS Name Resolution after failover 1. On the Start menu, click Run. 2. In the Run dialog box, type \\mycluster.mwtraders.msft\public 3. Windows Explorer opens and you can view the contents of the public folder. Demonstration 10 To test Active Directory Shared Folders after failover 1. On your desktop, double-click My Network Places. 2. In My Network Places, double-click Entire Network. 3. In the Entire Network window, click entire contents from the left side of the screen. 4. In the Entire Network window, double-click Directory. 5. In the Directory window, double-click nwtraders. 6. In the ntds://nwtraders.msft window, double-click Users. 7. In the ntds://nwtraders.msft/Users window, double-click Public. 8. Windows Explorer opens the contents of the public share on mycluster.
  8. viii Module 2: Concepts of Server Clusters Multimedia Presentation This section provides multimedia presentation procedures that do not fit in the margin notes or are not appropriate for the student notes. Microsoft Windows 2000 Cluster Service To prepare for the multimedia presentation 1. Preview the video and note where the information covered appears in the module (both in the list of definitions and in the greater detail pages that follow). 2. Add questions about the video and server clusters that may be especially relevant to your audience. 3. Make sure that you control the questions and discussions so that students do not expect the animation to be the equivalent of the entire module contents. Its purpose is to provide a broad overview to orient students to the materials that will follow. Module Strategy Use the following strategy to present this module: Introduction to Server Clusters The intent of this introduction is to give students a history of server cluster techniques and explain the differences between the model that Cluster service uses and two other options. It also provides an opportunity to emphasize the key benefits of server clusters: availability and scalability. • Clustering Techniques: Note the difference between a shared everything model and a shared nothing model, and how Cluster service utilizes the shared nothing model. • Availability and Scalability: Students should understand the differences between availability and scalability and how Cluster service improves availability and scalability. Multimedia: Introduction to Microsoft Windows 2000 Cluster Service Emphasize the shared nothing model and how it relates to the video, and how the application’s data is stored on the cluster disk.
  9. Module 2: Concepts of Server Clusters ix Key Concepts of a Server Cluster The list of key concepts that opens this section is designed to provide a brief description of the concepts that students will need to know to successfully install and administer a server cluster. The information in this section is foundational to the rest of the Cluster service portion of the course. Take time to process questions and check for understanding. • Cluster Disks. The cluster disks, also known as shared disks, are based on a shared nothing model. Only one node at a time has access to the disk. • Quorum Resource. The quorum is a vital part of Cluster service. Students need to understand what is stored in the quorum, how the nodes interact with the quorum through arbitration, and the data a node can get after a restart from the quorum recovery logs. • Cluster Communications. Cluster service communicates with clients over a public network, between nodes over a private network and can use a mixed network for a private network failover. • Groups and Resources. Students need to understand that groups are a logical collection of resources. You can add many resources to a group. You can take resources offline but they may have dependencies that will also bring other resources offline. • Resource Dependency Trees. Consultants often use diagrams of dependency trees to help their customers understand the concept of dependencies and how important they are to Cluster service. • Virtual Servers. A virtual server consists of a virtual IP address and a virtual name resource. Clients gain access to cluster resources through virtual servers. Students need to understand the relationship between the resources and the virtual servers. • Virtual Server Name Resolution. Clients access a virtual server as if it were a physical server on the network. Stress the importance of proper name resolution so that clients can always access the virtual server no matter which node is controlling the virtual server. • Failover and Failback. The key concept to keep applications and resources available is the ability for Cluster service to fail over a group from one node to another. Demonstration: Cluster Concepts This demonstration reinforces the concepts presented to the students in this section. Key points of the demo are name resolution to a virtual server and failover of a resource.
  10. x Module 2: Concepts of Server Clusters Choosing a Server Cluster Configuration The table on the first page of this section provides a reference point for the descriptions of the four configurations which follow. Ask students for examples of how they might use each of the configurations in their environments, or why they would not. • Active/Passive Configuration. Only one node is doing work in the cluster. The other node is waiting for the first node to fail. • Active/Active Configuration. Both nodes are performing work in the cluster, but have the capacity to handle all of the resources in case one node fails. • Hybrid Configuration. If a node is doing work outside the cluster, it is referred to as a hybrid configuration in either an active/active or active/passive configuration. • Single Node Virtual Server. This configuration is ideal for server consolidation because one physical server can control many virtual servers. Applications and Services on Server Clusters This section covers the information that students will need to decide which applications and services they will run in a server cluster. Make sure students understand the difference between cluster-aware and cluster- unaware applications and services. File and print shares benefit especially from the failover feature of Cluster service. The material on identifying performance limitations is not intended to be a complete planning guide for allocating resources in a server cluster, but should be explained as an issue that students will need to consider when installing Cluster service and adding services and applications to existing server clusters. • Applications. Students need to know the difference between cluster- aware and cluster-unaware applications. To run on Cluster service, you must configure cluster-unaware applications as generic resource types. • Services. The services that come with Microsoft Windows 2000 that can run on a server cluster are DFS, DHCP, and WINS. Cluster-aware and cluster-unaware services have the same characteristics as covered in the page on applications. • File and Print Shares. An excellent use for Cluster service is for highly- available file and print shares. • Identifying Performance Limitations. Students need to understand that the dynamics of a node’s performance could change depending on what groups the node controls. Lab Setup There are no lab setup requirements that affect replication or customization.
  11. Module 2: Concepts of Server Clusters 1 Overview Topic Objective To provide an overview of the module topics and Introduction to Server Clusters objectives. Lead-in Key Concepts of a Server Cluster In this topic we will talk about the features and key Choosing a Server Cluster Configuration concepts of server clusters. Applications and Services on Server Clusters *****************************ILLEGAL FOR NON-TRAINER USE****************************** This module provides an explanation of server cluster terms and key concepts. Topics include considerations for choosing cluster configuration options and determining which applications and services will be included in the server cluster. Information that is unique to the installation of Microsoft® Cluster service is covered, such as naming and addressing conventions and how resources and groups function within a server cluster. After completing this module, you will be able to: Explain the features of clustering technologies. Define the key terms and concepts of a server cluster. Choose a server cluster configuration. Describe how Cluster service supports applications and services.
  12. 2 Module 2: Concepts of Server Clusters Introduction to Server Clusters Topic Objective To introduce the concept and benefits of clustering technologies. Lead-in A server cluster is a group of computers and storage devices that work together and are accessed by clients as a single system. *****************************ILLEGAL FOR NON-TRAINER USE****************************** A server cluster is a group of computers and storage devices that work together and can be accessed by clients as a single system. The individual computers in the cluster are referred to as nodes, and they act together to provide automatic recovery from failure of clustered services and applications. There are two types of network communications in a server cluster. The nodes communicate with each other over a high performance, reliable network, and share one or more common storage devices. Clients communicate to logical servers, referred to as virtual servers, to gain access to grouped resources, such as file or print shares, services such as Windows Internet Name Service (WINS), and applications like Microsoft Exchange Server. When a client connects to the virtual server, the server routes the request to the node controlling the requested resource, service, or application. If the controlling node fails, any clustered services or applications running on the failed node will restart on a surviving designated node. There are three types of clustering techniques commonly used: shared everything, mirrored servers, and shared nothing. Microsoft Cluster Service uses the shared nothing model. You can configure server clusters to address both availability and scalability issues. The failover capability of Microsoft Cluster Service makes resources more available than in a non-clustered environment. It is also an economical way to scale up when you need greater performance.
  13. Module 2: Concepts of Server Clusters 3 Clustering Techniques Topic Objective To identify the differences between three server cluster Shared Everything Model models. Lead-in Mirrored Servers There are three commonly used server cluster models. Shared Nothing Model *****************************ILLEGAL FOR NON-TRAINER USE****************************** There are a variety of cluster implementation models that are used widely in the computer industry. Common models are shared everything, mirrored servers, and shared nothing. It is possible for a cluster to support both the shared everything model and the shared nothing model. Typically, applications that require only limited shared access to data work best in the shared everything model. Applications that require maximum scalability will benefit from the shared nothing cluster model. Shared Everything Model In the shared everything, or shared device model, software running on any computer in the cluster can gain access to any hardware resource connected to any computer in the cluster (for example, a hard drive, random access memory (RAM), and CPU). The shared everything server clusters permit every server to access every disk. Allowing access to all of the disks originally required expensive cabling and switches, plus specialized software and applications. If two applications require access to the same data, much like a symmetric multiprocessor (SMP) computer, the cluster must synchronize access to the data. In most shared device cluster implementations, a component called a Distributed Lock Manager (DLM) is used to handle this synchronization. The Distributed Lock Manager (DLM) The Distributed Lock Manager (DLM) is a service running on the cluster that keeps track resources within the cluster. If multiple systems or applications attempt to reference a single resource, the DLM recognizes and resolves the conflict. However, using a DLM introduces a certain amount of overhead into the system in the form of additional message traffic between nodes of the cluster in addition to the performance loss due to serialized access to hardware resources. Shared everything clustering also has inherent limits on scalability, because DLM contention grows geometrically as you add servers to the cluster.
  14. 4 Module 2: Concepts of Server Clusters Mirrored Servers An alternative to the shared everything and shared nothing models is to run software that copies the operating system and the data to a backup server. This technique mirrors every change from one server to a copy of the data on at least one other server. This technique is commonly used when the locations of the servers are too far apart for the other cluster solutions. The data is kept on a backup server at a disaster recovery site and is synchronized with a primary server. However, a mirrored server solution cannot deliver the scalability benefits of clusters. Mirrored servers may never deliver as high a level of availability and manageability as shared-disk clustering, because there is always a finite amount of time during the mirroring operation in which the data at both servers is not identical. Shared Nothing Model The shared nothing model, also known as the partitioned data model, is designed to avoid the overhead of the DLM in the shared everything model. In this model, each node of the cluster owns a subset of the hardware resources that make up the cluster. As a result, only one node can own and access a hardware resource at a time. A shared-nothing cluster has software that can transfer ownership to another node in the event of a failure. The other node takes ownership of the hardware resource so that the cluster can still access it. The shared nothing model is asymmetric. The cluster workload is broken down into functionally separate units of work that different systems performed in an independent manner. For example, Microsoft SQL Server™ may run on one node at the same time as Exchange is running on the other. In this model, requests from client applications are automatically routed to the system that owns the resource. This routing extends to server applications that are running on a cluster. For example, if a cluster application such as Internet Information Services (IIS) needs to access a SQL Server database on another node, the node it is running on passes the request for the data to the other node. Remote procedure call (RPC) provides the connectivity between processes that are running on different nodes. A shared nothing cluster provides the same high level of availability as a shared everything cluster and potentially higher scalability, because it does not have the inherent bottleneck of a DLM. An added advantage is that it works with standard applications because there are no special disk access requirements. Examples of shared nothing clustering solutions include Tandem NonStop, Informix Online/XPS, and Microsoft Windows 2000 Cluster service. Note Cluster service uses the shared nothing model. By default, Cluster service does not allow simultaneous access from both nodes to the shared disks or any resource. Cluster service can support the shared device model as long as the application supplies a DLM.
  15. Module 2: Concepts of Server Clusters 5 Availability and Scalability Topic Objective To describe the two key benefits of Cluster service. Availability Lead-in The failover capability of Cluster Service Improves Availability of Applications and Cluster service makes Services resources more available than in a nonclustered Scalability environment. It is also an economic way to scale up Cluster Service Improves Scalability by Adding More when you need greater Computers to the Cluster performance. *****************************ILLEGAL FOR NON-TRAINER USE****************************** Microsoft Cluster service makes resources, such as services and applications, more available by providing for restart and failover of the resource. Another benefit of Cluster service is that it provides greater scalability of the resource because you can separate applications and services to run on different servers. Availability When a system or component in the cluster fails, the cluster software responds by dispersing the work from the failed system to the remaining systems in the cluster. Cluster service improves the availability of client/server applications by increasing the availability of server resources. Using Cluster service, you can set up applications on multiple nodes in a cluster. If one node fails, the applications on the failed node are available on the other node. Throughout this process, client communications with applications usually continue with little or no interruption. In most cases, the interruption in service is detected in seconds, and services can be available again in less than a minute (depending on how long it takes to restart the application). Clustering provides high availability with static load balancing, but it is not a fault tolerant solution. Fault tolerant solutions offer error-free, nonstop availability, usually by keeping a backup of the primary system. This backup system remains idle and unused until a failure occurs, which makes this an expensive solution.
  16. 6 Module 2: Concepts of Server Clusters Scalability When the overall load exceeds the capabilities of the systems in the cluster, instead of replacing an existing computer with a new one with greater capacity, you can add additional hardware components to increase the node’s performance, while maintaining availability of applications that are running on the cluster. Using Microsoft clustering technology, it is possible to incrementally add smaller, standard systems to the cluster as needed to meet overall processing power requirements. Clusters are highly scalable; you can add CPU, input/output (I/O), storage, and application resources incrementally to efficiently expand capacity. A highly scalable solution creates reliable access to system resources and data, and protects your investment in both hardware and software resources. Server clusters are affordable because they can be built with commodity hardware (high-volume components that are relatively inexpensive).
  17. Module 2: Concepts of Server Clusters 7 Multimedia: Microsoft Windows 2000 Cluster Service Topic Objective To introduce the animation which depicts the functions and terms of server clusters. Lead-in This video shows an overview of Cluster service. *****************************ILLEGAL FOR NON-TRAINER USE****************************** In this video you will learn the basic functionality of Cluster service. At the end of this video, you should be able to answer the following questions. What is a node? Two or more servers that are connected by a shared bus, which is running Cluster service. _______________________________________________________________ _______________________________________________________________ Where is the application data stored? On the cluster disk. _______________________________________________________________ _______________________________________________________________
  18. 8 Module 2: Concepts of Server Clusters What is a private network used for in a server cluster? Provides intracluster communications between the nodes, which are called heartbeats. _______________________________________________________________ _______________________________________________________________ What happens when an application fails? Cluster service tries to restart the application on the same node. If the application fails to restart, control of the resource is automatically transferred to the other node. _______________________________________________________________ _______________________________________________________________
  19. Module 2: Concepts of Server Clusters 9 Key Concepts of a Server Cluster Topic Objective Server Cluster To identify the key concepts of a server cluster. Node A Node A Lead-in A Group of Resources A server cluster has physical components and Private Client logical resources. File Share Private Client File Share Network Network Quorum Disk 1 Virtual Virtual Disk 1 Server Server Print Share Print Share Node B Node B Public Public Network Network *****************************ILLEGAL FOR NON-TRAINER USE****************************** Server cluster architecture consists of physical cluster components and logical Delivery Tip cluster resources. Microsoft Cluster service is the software that manages all of This page is intended to the cluster-specific activity. give a brief overview with a visual illustration of the key Physical components provide data storage and processing for the logical cluster concepts of server clusters. resources. Physical components are nodes, cluster disks, and communication With the exception of nodes, networks. Logical cluster resources are groups of resources, such as Internet each item is covered in Protocol (IP) addresses and virtual server names, and services such as WINS. greater detail in the Clients interact with the logical cluster resources. following pages. Nodes Nodes are the units of management for the server cluster. They are also referred to as systems and the terms are used interchangeably. A node can be online or offline, depending on whether it is currently in communication with the other cluster nodes. Note Windows 2000 Advanced Server supports two node server clusters. Windows 2000 Datacenter supports four node server clusters. Cluster Disks Cluster disks are shared hard drives to which both server cluster nodes attach by means of a shared bus. You store data for file and print shares, applications, resources, and services on the shared disks.
  20. 10 Module 2: Concepts of Server Clusters Quorum Resource The quorum resource plays a vital role in allowing a node to form a cluster and in maintaining consistency of the cluster configuration for all nodes. The quorum resource holds the cluster management data and recovery log, and arbitrates between nodes to determine which node controls the cluster. The quorum resource resides on a shared disk. It is best to use a dedicated cluster disk for the quorum resource, so that it will not be affected by the failover policies of other resources, or by the space that other applications require. It is recommended that the quorum be on a disk partition of at least 500 MB. Cluster Communications A server cluster communicates on a public, private, or mixed network. The public network is used for client access to the cluster. The private network is used for intracluster communications, also referred to as node-to-node communications. The mixed network can be used for either type of cluster communications. One of the types of communications on the private network monitors the health of each node in the cluster. Each node periodically exchanges IP packets with the other node in the cluster to determine if both nodes are operational. This process is referred to as sending heartbeats. Resources Resources are the basic unit that Cluster service manages. Examples of resources are physical hardware devices, such as disk drives, or logical items, such as IP addresses, network names, applications, and services. A cluster resource can run only on a single node at any time, and is identified as online when it is available for a client to use. Groups Groups are a collection of resources that Cluster service manages as a single unit for configuration purposes. Operations that are performed on groups, such as taking groups offline or moving them to another node, affect all of the resources that are contained within that group. Ideally, a group will contain all of the elements that are needed to run a specific application, and for client systems to connect to the application. Virtual Servers Virtual servers have server names that appear as physical servers to clients. Cluster service uses a physical server to host one or more virtual servers. Each virtual server has an IP address and a network name that are published to clients on the network. Users access applications or services on virtual servers in the same way that they would if the application or service were on a physical server. Failover and Failback Failover is the process of moving a group of resources from one node to another in case of a failure of a node, or one of the resources in the group. Failback is the process of returning a group of resources to the node on which it was running before the failover occurred.
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