Clustering Technologies
-
Upload
vinod-hanumantharayappa -
Category
Documents
-
view
217 -
download
0
Transcript of Clustering Technologies
8/6/2019 Clustering Technologies
http://slidepdf.com/reader/full/clustering-technologies 1/5
Clustering TechnologiesUpdated: March 28, 2003
Clustering Technologies
The clustering technologies in products in the Microsoft Windows Server 2003 operating system are
designed to help you achieve high availability and scalability for applications that are critically
important to your business. These applications include corporate databases, e-mail, and Web-based
services such as retail Web sites. By using appropriate clustering technologies and carefully
implementing good design and operational practices (for example, configuration management and
capacity management), you can scale your installation appropriately and ensure that your applications
and services are available whenever customers and employees need them.
High availability is the ability to provide user access to a service or application for a high percentage
of scheduled time by attempting to reduce unscheduled outages and mitigate the impact of scheduled
downtime for particular servers. Scalability is the ability to easily increase or decrease computing
capacity. A cluster consists of two or more computers working together to provide a higher level of
availability, scalability, or both than can be obtained by using a single computer. Availability is
increased in a cluster because a failure in one computer results in the workload being redistributed to
another computer. Scalability tends to be increased, because in many situations it is easy to change
the number of computers in the cluster.
Windows Server 2003 provides two clustering technologies: server clusters and Network Load
Balancing (NLB). Server clusters primarily provide high availability; Network Load Balancing provides
scalability and at the same time helps increase availability of Web-based services.
Your choice of cluster technologies (server clusters or Network Load Balancing) depends primarily on
whether the applications you run have long-running in-memory state:
• Server clusters are designed for applications that have long-running in-memory state or
frequently updated data. These are called stateful applications. Examples of stateful
applications include database applications such as Microsoft SQL Server 2000 and messaging
applications such as Microsoft Exchange Server 2003.
Server clusters can combine up to eight servers.
• Network Load Balancing is intended for applications that do not have long-running in-
memory state. These are called stateless applications. A stateless application treats each
client request as an independent operation, and therefore it can load-balance each request
independently. Stateless applications often have read-only data or data that changes
infrequently. Web front-end servers, virtual private networks (VPNs), and File Transfer
Protocol (FTP) servers typically use Network Load Balancing. Network Load Balancing clusters
can also support other TCP- or UDP-based services and applications.
Network Load Balancing can combine up to 32 servers.
In addition, with Microsoft Application Center 2000 Service Pack 2, you can create another type of
cluster, a Component Load Balancing cluster. Component Load Balancing clusters balance the load
between Web-based applications distributed across multiple servers and simplify the management of
those applications. Application Center 2000 Service Pack 2 can be used with Web applications built on
either the Microsoft Windows 2000 or Windows Server 2003 operating systems.
Multitiered Approach for Deployment of Multiple Clustering Technologies
8/6/2019 Clustering Technologies
http://slidepdf.com/reader/full/clustering-technologies 2/5
Microsoft does not support the configuration of server clusters and Network Load Balancing clusters on
the same server. Instead, use these technologies in a multitiered approach.
Clustering Technologies Architecture
A cluster consists of two or more computers (servers) working together. For server clusters, the
individual servers are called nodes. For Network Load Balancing clusters, the individual servers are
called hosts.
Basic Architecture for Server Clusters
The following diagram shows a four-node server cluster of the most common type, called a single
quorum device cluster. In this type of server cluster, there are multiple nodes with one or more
cluster disk arrays (often called the cluster storage) and a connection device (bus). Each of the disks
in the disk array are owned and managed by only one node at a time. The quorum resource on the
cluster disk array provides node-independent storage for cluster configuration and state data, so that
each node can obtain that data even if one or more other nodes are down.
Four-Node Server Cluster Using a Single Quorum Device
Basic Architecture for Network Load Balancing Clusters
The following diagram shows a Network Load Balancing cluster with eight hosts. Incoming client
requests are distributed across the hosts. Each host runs a separate copy of the desired server
application, for example, Internet Information Services. If a host failed, incoming client requests
would be directed to other hosts in the cluster. If the load increased and additional hosts were
needed, you could add them dynamically to the cluster.
Network Load Balancing Cluster with Eight Hosts
8/6/2019 Clustering Technologies
http://slidepdf.com/reader/full/clustering-technologies 3/5
Clustering Technologies Scenarios
This section describes the most common scenarios for using server clusters and Network Load
Balancing.
Scenarios for Server Clusters
This section provides brief descriptions of some of the scenarios for server cluster deployment. The
scenarios cover three different aspects of server cluster deployment:
• The applications or services on the server cluster.
• The type of storage option: SCSI, Fibre Channel arbitrated loops, or Fibre Channel switched
fabric.
• The number of nodes and the ways that the nodes can fail over to each other.
Applications or Services on a Server Cluster
Server clusters are usually used for services, applications, or other resources that need high
availability. Some of the most common resources deployed on a server cluster include:
• Printing
• File sharing
• Network infrastructure services. These include the DHCP service and the WINS service.
• Services that support transaction processing and distributed applications. These
services include the Distributed Transaction Coordinator (DTC) and Message Queuing.
• Messaging applications. An example of a messaging application is Microsoft Exchange
Server 2003.
8/6/2019 Clustering Technologies
http://slidepdf.com/reader/full/clustering-technologies 4/5
• Database applications. An example of a database application is Microsoft SQL Server 2000.
Types of Storage Options
A variety of storage solutions are currently available for use with server clusters. As with all hardware
that you use in a cluster, be sure to choose solutions that are listed as compatible with Windows
Server 2003, Enterprise Edition, or Windows Server 2003, Datacenter Edition. Also be sure to follow
the vendor’s instructions closely.
The following table provides an overview of the three types of storage options available for server
clusters running Windows Server 2003, Enterprise Edition, or Windows Server 2003, Datacenter
Edition:
Storage Options for Server Clusters
Storage Option Maximum Number of Supported Nodes
SCSI Two
Fibre Channel arbitrated loop Two
Fibre Channel switched fabric Eight
Number of Nodes and Failover Plan
Another aspect of server cluster design is the number of nodes used and the plan for application
failover:
• N-node Failover Pairs. In this mode of operation, each application is set to fail over
between two specified nodes.
• Hot-Standby Server /N+I. Hot-standby server operation mode reduces the overhead of
failover pairs by consolidating the “spare” (idle) node for each pair into a single node,
providing a server that is capable of running the applications from each node pair in the
event of a failure. This mode of operation is also referred to as active/passive.
For larger clusters, N+I mode provides an extension of the hot-standby server mode where N
cluster nodes host applications and I cluster nodes are spare nodes.
• Failover Ring. In this mode of operation, each node in the cluster runs an application
instance. In the event of a failure, the application on the failed node is moved to the next
node in sequence.
• Random. For large clusters running multiple applications, the best policy in some cases is to
allow the server cluster to choose the fail over node at random.
Scenarios for Network Load Balancing
This section provides brief descriptions of some of the scenarios for deployment of Network Load
Balancing. The scenarios cover three different aspects of Network Load Balancing deployment:
• The types of servers or services in Network Load Balancing clusters.
• The number and mode of network adapters on each host.
Types of Servers or Services in Network Load Balancing Clusters
In Network Load Balancing clusters, some of the most common types of servers or services are as
follows:
8/6/2019 Clustering Technologies
http://slidepdf.com/reader/full/clustering-technologies 5/5
• Web and File Transfer Protocol (FTP) servers.
• ISA servers (for proxy servers and firewall services).
• Virtual private network (VPN) servers.
• Windows Media servers.
• Terminal servers.
Number and Mode of Network Adapters on Each Network Load Balancing Host
Another aspect of the design of a Network Load Balancing cluster is the number and mode of the
network adapter or adapters on each of the hosts:
Number and Modeof Network
Adapters on EachHost Use
Single network
adapter in unicastmode
A cluster in which ordinary network communication among cluster hosts
is not required and in which there is limited dedicated traffic fromoutside the cluster subnet to specific cluster hosts.
Multiple networkadapters in unicastmode
A cluster in which ordinary network communication among cluster hostsis necessary or desirable. It is also appropriate when you want toseparate the traffic used to manage the cluster from the traffic
occurring between the cluster and client computers.
Single networkadapter in multicast
mode
A cluster in which ordinary network communication among cluster hostsis necessary or desirable but in which there is limited dedicated traffic
from outside the cluster subnet to specific cluster hosts.
Multiple networkadapters in multicast
mode
A cluster in which ordinary network communication among cluster hostsis necessary and in which there is heavy dedicated traffic from outside
the cluster subnet to specific cluster hosts.