Tài liệu Module 2: Concepts of Server Clusters doc

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

Module 2: Concepts of
Server Clusters


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Module 2: Concepts of Server Clusters iii

Instructor Notes
This module provides students with a brief overview of the different types of
server clusters and their key benefits of availability and scalability. A short
video gives an overview of how Cluster service functions, and introduces the
key terms and concepts, which are explained in the Key Concepts of a Server
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.

Presentation:
90 Minutes

Lab:
00 Minutes
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.
Module 2: Concepts of Server Clusters v

9. User Name:
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.

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.

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.

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.
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.
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.

Module 2: Concepts of Server Clusters 1

Overview

 Introduction to Server Clusters
 Key Concepts of a Server Cluster
 Choosing a Server Cluster Configuration
 Applications and Services on Server Clusters

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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.

Topic Objective
To provide an overview of
the module topics and
objectives.
Lead-in
In this topic we will talk
about the features and key
concepts of server clusters.
2 Module 2: Concepts of Server Clusters



 Introduction to Server Clusters

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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.
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.
Module 2: Concepts of Server Clusters 3

Clustering Techniques
 Shared Everything Model
 Mirrored Servers
 Shared Nothing Model

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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.
Topic Objective
To identify the differences
between three server cluster
models.
Lead-in
There are three commonly
used server cluster models.
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.

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.

Note
Module 2: Concepts of Server Clusters 5

Availability and Scalability
 Availability
 Cluster Service Improves Availability of Applications and
Services
 Scalability
 Cluster Service Improves Scalability by Adding More
Computers to the Cluster

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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.
Topic Objective
To describe the two key
benefits of Cluster service.
Lead-in
The failover capability of
Cluster service makes
resources more available
than in a nonclustered
environment. It is also an
economic way to scale up
when you need greater
performance.
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).
Module 2: Concepts of Server Clusters 7

Multimedia: Microsoft Windows 2000 Cluster Service

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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.
_______________________________________________________________
_______________________________________________________________
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.
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.
_______________________________________________________________
_______________________________________________________________

Module 2: Concepts of Server Clusters 9



 Key Concepts of a Server Cluster
Client
Client
Private
Network
Private

Network
Server Cluster
Quorum
Disk 1
A Group of Resources
Virtual
Server
Virtual
Server
Disk 1
Print Share
Print Share
File Share
File Share
Public
Network
Public
Network
Node A
Node A
Node B
Node B

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Server cluster architecture consists of physical cluster components and logical
cluster resources. Microsoft Cluster service is the software that manages all of
the cluster-specific activity.
Physical components provide data storage and processing for the logical cluster
resources. Physical components are nodes, cluster disks, and communication

networks. Logical cluster resources are groups of resources, such as Internet
Protocol (IP) addresses and virtual server names, and services such as WINS.
Clients interact with the logical cluster resources.
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.

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.
Topic Objective
To identify the key concepts
of a server cluster.
Lead-in
A server cluster has
physical components and
logical resources.
Delivery Tip
This page is intended to
give a brief overview with a
visual illustration of the key
concepts of server clusters.
With the exception of nodes,
each item is covered in

greater detail in the
following pages.
Note
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.
Module 2: Concepts of Server Clusters 11

Cluster Disks
Node A
Node A
Node B
Node B
Disk 4
Disk 3
Disk 2
Disk 1

Quorum

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Each node must have a connection to a shared storage area where shared cluster
data, such as configuration data, is stored. This shared storage area is referred to
as the cluster disk. The cluster can gain access to a cluster disk through a Small
Computer System Interface (SCSI) bus or a Fibre Channel bus. In addition,
services and applications that the cluster provides should keep shared data, such
as Web pages, on the cluster disk on the shared bus.
Cluster service is based on the shared nothing model of clustering. The shared
nothing model allows the Windows 2000 cluster file system model to support
the native NTFS file system, rather than requiring a dedicated cluster file
system.

The cluster disks must be NTFS and basic disks.

A single cluster member controls each file system partition at any instant in
time. However, because a node places a SCSI reserve on a cluster disk rather
than a partition, the same node must own all of the partitions on the same
physical disk at any given time. Each node can reserve a separate disk on the
same shared bus, so you can divide the cluster disks on the bus between the
nodes in the cluster.

For high-end configurations, you can achieve additional I/O scaling through
distributed striping technology such as RAID 5. Using distributed striping
technology means that below a file system partition on a single node, that
partition can actually be a stripe set whose physical disks span multiple disks.
Such striping must be hardware RAID. Cluster service does not support any
software fault tolerant RAID arrays.

Topic Objective
To explain the use of cluster
disks for storing shared
cluster data.
Lead-in
The nodes in a cluster
access data from a shared
storage area.
Delivery Tip
SCSI and Fibre Channel
comparisons are covered in
Course 2087A, Module 3,
“Preparing for Cluster
Service Installation.”
Note
12 Module 2: Concepts of Server Clusters

Quorum Resource
 Data Storage
 Arbitration
 Quorum Ownership
 Updates for Nodes Coming Online

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Each cluster has a special resource known as the quorum resource. You specify
an initial location for the quorum resource when you install the first node of a
cluster. You can use the cluster administration tools to change the quorum
location to a different storage resource.
The quorum resource contains cluster configuration files and provides two vital

functions: data storage and arbitration. Only one node at a time controls the
quorum. Upon startup of the cluster, Cluster service uses the quorum resource
recovery logs for node updates.
For example: If Node B is offline and Node A makes a change to the cluster,
the change is saved in the registry of Node A and also to the cluster
configuration files on the quorum. If Node A goes offline and Node B starts,
Node B will be updated from the cluster configuration files on the quorum.
Data Storage
The quorum resource is vital to the successful operation of a cluster because it
stores cluster management data, such as the configuration database and
recovery logs for changes that are made to cluster data. It must be available
when you form the cluster, and whenever you change the configuration
database. All of the nodes of the cluster have access to the quorum resource by
means of the owning node.

To ensure the availability of the cluster, it is recommended that the
quorum be on a Redundant Array of Independent Disks (RAID) 5 array.

Topic Objective
To describe the function of
the quorum resource in a
server cluster.
Lead-in
The quorum resource is
unique to server clusters.
Note
Module 2: Concepts of Server Clusters 13

Arbitration
The Cluster service uses the quorum resource to decide which node owns the

cluster. Arbitration refers to the decision-making function of the quorum
resource if both cluster nodes independently try to take control of the cluster.
Consider the following situation in a two-node cluster. The networks that are
providing communication between Nodes A and B fail. Each node assumes that
the other node has failed, and attempts to operate the cluster as the remaining
node. Arbitration determines which node owns the quorum. The node that does
not own the quorum must take its resources offline. The node that controls the
quorum resource then brings all of the cluster resources online.
Quorum Ownership
Only one node can control the quorum. When a node restarts, Cluster service
determines whether the owner of the quorum is online. If there is no owner of
the quorum, Cluster service assigns ownership to the starting node. If Cluster
service finds that another node is online and owns the quorum resource, it will
join the starting node to the cluster, and will not assign the ownership of the
quorum to this node.
Updates for Nodes Coming Online
When a node that has been offline rejoins a cluster, Cluster service must update
the node's private copy of the cluster database with any changes it may not have
received while it was offline. When a node rejoins a cluster, Cluster service can
retrieve the data from the other active nodes. However, when both nodes are
offline, the first node to come online will form a cluster and will need to
retrieve any possible changes. Cluster service uses the recovery logs of the
quorum resource to update any changes to the node's cluster database.

Do not modify the access permissions on the disk that contains the
quorum resource. Cluster service must have full access to the quorum log.
Cluster service uses the quorum log file to write all of the cluster state and
configuration changes that cannot be updated if the other node is offline. For
this reason, you should never restrict either node’s access to the folder \MSCS
on the quorum disk which contains the quorum log.

Caution
14 Module 2: Concepts of Server Clusters

Cluster Communications
 Private Network
 Public Network
 Mixed Network

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ILLEGAL FOR NON-TRAINER USE******************************
It is strongly recommended that a cluster have more than one network
connection. A single network connection threatens the cluster with a single
point of failure. There are three options for network configurations, private,
public, and mixed. Each network configuration requires its own dedicated
network card.
Private Network
Cluster nodes need to be consistently in communication over a network to
ensure that both nodes are online. Cluster service can utilize a private network
that is separate from client communications. Once a connection is configured as
a private network it can only be used for internal cluster communications, and is
known as a private network or interconnect. The private network will be the
default route for node-to-node communication. The cluster cannot use a private
network for client-to-node communication.
Heartbeats
Each node in a cluster periodically exchanges sequenced User Datagram
Protocol (UDP) datagrams with the other node in the cluster to determine if it is
up and running correctly, and to monitor the health of a network link. This
process is referred to as sending heartbeats.

Public Network
The public network connection is used as a dedicated client-to-node
communication network. The cluster cannot use the public network for node-to-
node communication.
Topic Objective
To describe the three types
of network communications
in a server cluster.
Lead-in
You should plan to have at
least two network
connections for cluster
communications.
Delivery Tip
Heartbeats and other types
of cluster communications
are covered in detail in
Course 2087A, Module 3,
“Preparing for Cluster
Service Installation.”
Module 2: Concepts of Server Clusters 15

Mixed Network
Another configuration option is to create a network that is used for both private
and public communication. This is called a mixed network. Using a mixed
network does not change the recommendation for two networks.

The recommended configuration for server clusters is a dedicated
private network for node-to-node communication and a mixed network. The
mixed network acts as a backup connection for node-to-node communication

should the private network fail. This configuration avoids having any single
point of network failure.

Importan
t