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CLUSTERING AND AVAILABILITY

Chapter 11

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OVERVIEW

Describe the clustering capabilities of Microsoft Windows Server 2003.

Understand how to create clusters with Windows Server 2003.

Plan a high-availability solution that uses clustering services.

Plan a high-availability solution that uses Network Load Balancing.

Estimate your organization’s availability requirements.

Determine which type of cluster to use for your applications.

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OVERVIEW (CONTINUED)

Understand the differences among the four Network Load Balancing operational modes

List the steps involved in deploying a Network Load Balancing cluster

Monitor Network Load Balancing using Windows Server 2003 tools

List the shared storage hardware systems supported by Windows Server 2003

Describe the quorum models you can use in a server cluster

List the steps involved in creating a server cluster

Describe the different types of failover policies you can use with server clusters

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UNDERSTANDING CLUSTERING

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CLUSTERING TYPES

Server clusters

Network Load Balancing clusters

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SERVER CLUSTERS

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NETWORK LOAD BALANCING

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NETWORK LOAD BALANCING AND REPLICATION

The key difference between Network Load Balancing and server clustering is that in a Network Load Balancing cluster each system in the cluster maintains its own data set.

Network Load Balancing is unsuitable for applications that have a very fluid data set.

Manual replication of data between nodes in a Network Load Balancing cluster should be occasional, rather than continuous.

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DESIGNING A CLUSTERING SOLUTION

What are you protecting against? Software failure

Hardware failure

Site failure

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ESTIMATING AVAILABILITY REQUIREMENTS

The degree of availability you require depends on a variety of factors: Nature of the applications you are running

Size, location, and distribution of your user base

Role of the applications in your organization

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SCALING CLUSTERS

Scale up—Improve performance of systems by installing a more powerful processor, adding random access memory (RAM), and higher-performance disk subsystems.

Scale out—Add servers to the cluster to increase overall processing power.

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SCALABILITY IN THE REAL WORLD

Scalability of a cluster is limited by the capabilities of the operating system: Scaling out depends on the clustering

limitations of the operating systems used in the cluster.

Scaling up depends on the maximum supported hardware configuration of the operating systems used in the cluster.

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NUMBERS OF CLUSTERS

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COMBINING CLUSTERING TECHNOLOGIES

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DISPERSING CLUSTERS

Geographic separation provides higher availability in situations such as the following: Natural disaster (flood, earthquake, tornado)

Power failure, rolling blackouts

Theft, vandalism, terrorism

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USING NETWORK LOAD BALANCING

Easier to install, configure, and maintain than server clustering

Does not require additional storage hardware

Does not require additional software

Managed by using the Network Load Balancing Manager application

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UNDERSTANDING NETWORK LOAD BALANCING

Each Network Load Balancing cluster can consist of up to 32 servers.

A virtual network adapter acts as an intermediary between the physical network interface and the protocol stack.

Clients address their application requests to the cluster Internet Protocol (IP) address instead of to an individual server’s IP address.

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NETWORK LOAD BALANCING CLUSTERING AND THE DOMAIN NAME SYSTEM

The Domain Name System (DNS) resource records for systems in a cluster must be changed so that they supply clients with the cluster IP address, not the original server IP addresses.

An algorithm associated with the virtual network adapter determines which requests should be answered and which should be ignored.

All nodes in the cluster receive the request, but only the node whose turn it is actually answers the request.

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PLANNING A NETWORK LOAD BALANCING DEPLOYMENT

Using Network Load Balancing requires that you create a plan for the infrastructure that will support your cluster servers.

The high availability provided by Network Load Balancing must be further supported by fault-tolerant implementations of other networking equipment.

The security of your cluster servers and the rest of your internal network must be considered during the planning phase.

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NETWORK LOAD BALANCING OPERATIONAL MODES

Unicast mode—Servers in the cluster can communicate only with each other if more than one network interface is installed in the server.

Multicast mode—Servers with one network card can communicate with each other, but any routers on the network must support multicast Media Access Control (MAC) addresses.

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NETWORK LOAD BALANCING HEARTBEATS

Servers in a Network Load Balancing cluster determine independently whether to process an incoming request.

Servers in a Network Load Balancing cluster transmit heartbeat messages to let the other servers in the cluster know they are running and operational.

Heartbeats are the only cluster-related communication between servers in a Network Load Balancing cluster.

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DEPLOYING A NETWORK LOAD BALANCING CLUSTER

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MONITORING NETWORK LOAD BALANCING

Monitoring Network Load Balancing clusters can be performed using Network Load Balancing Manager

Event Viewer

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USING NETWORK LOAD BALANCING MANAGER

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USING EVENT VIEWER

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USING Nlb.exe

Command-line utility used to configure and manage Network Load Balancing clusters

Enables commands to be placed into scripts and batch files

Uses the same command options as the WLBS utility provided in earlier versions of Windows server operating systems

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DESIGINING A SERVER CLUSTER

Designing a server cluster deployment

Planning a server cluster hardware configuration

Creating an application deployment plan

Selecting a quorum model

Creating a server cluster

Configuring failover policies

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DESIGINING A SERVER CLUSTER DEPLOYMENT

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PLANNING A SERVER CLUSTER HARDWARE CONFIGURATION

The computers running Windows Server 2003 that you use to build a server cluster must Use the same edition of the Windows

operating system

Use the same processor architecture

Have at least one standard network connection

Have a separate connection to the shared storage device

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USING SMALL COMPUTER SYSTEM INTERFACE

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USING FIBRE CHANNEL

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CREATING AN APPLICATION DEPLOYMENT PLAN

Single-instance applications—Applications that can run on no more than one server at a time, using a given configuration

Multiple-instance applications—Applications in which duplicated code can run on multiple nodes in a cluster or in which the code can be partitioned

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DEPLOYING SINGLE-INSTANCE APPLICATIONS

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CAPACITY PLANNING

The servers in your cluster must have sufficient memory and enough processing capabilities to function adequately in a worst-case scenario.

Insufficient capacity planning can negate the benefit of using a cluster.

Testing and evaluation should include peak load tests to simulate realistic use.

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DEPLOYING MULTIPLE-INSTANCE APPLICATIONS

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SELECTING A QUORUM MODEL

Single-node cluster

Single-quorum device cluster

Majority node set cluster

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CREATING A SERVER CLUSTER

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CLUSTER RESOURCES

A cluster resource is any physical or logical element the Cluster service can manage by bringing it online or offline and moving it to a different node.

Cluster resources supported by server clusters running Windows Server 2003 include storage devices, configuration parameters, scripts, and applications.

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CONFIGURING FAILOVER POLICIES

Failover pairs

Hot-standby server

N+I

Failover ring

Random

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SUMMARY

A cluster is a group of servers appearing to users as a single resource that provides high availability, reliability, and scalability for specific applications.

A server cluster is a group of servers running a stateful application, such as a database server, and sharing a common data store.

A Network Load Balancing cluster is a group of servers running a stateless application, each of which has an identical independent data store.

Network Load Balancing works by creating a virtual network adapter with IP and MAC addresses that represent the cluster as a single unit.

Network Load Balancing can be run in either unicast mode or multicast mode.

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SUMMARY (CONTINUED)

Using multiple adapters in each server in a cluster can prevent network performance degradation.

A server cluster requires a storage resource shared by the nodes in the cluster.

In a server cluster, the quorum is a storage resource that contains cluster configuration data.

You can configure a cluster to use various failover policies.

To create and manage server clusters, you use the Cluster Administrator application. To manage Network Load Balancing clusters, you use Network Load Balancing Manager.