CHAPTER 7
MICROSOFT EXCHANGE 2000 SERVER IN
CLUSTERED
ENVIRONMENTS
Clustering is an advanced technology that allows you to design high availability solutions for your
enterprise-level applications. Clustering is often brought into play in business-critical services such
as messaging in an enterprise environment.
Lesson 1:
Cluster Service Architecture
A cluster is basically a group of servers that appear as a single virtual server. A virtual server
corresponds to a generic IP address and a network name, and allows your users to access all
the resources in the cluster, including Exchange 2000 Services, without having to know the names
of the individual nodes.
By grouping two or more computers together in a cluster, you can minimize system downtime
caused by software, network, and hardware failures.
Server Clusters in Exchange 2000 Environments
Clustering is a mature technology available for all popular network operating systems, including
Solaris and Windows 2000.
Despite assumptions and desires, it is impossible to achieve these goals with Windows 2000
Cluster service. Although it is not a 100% perfect solution, clustering does reduce the number
of potential single points of failure and thereby improves service availability.
The advantage of clustering, however, is that your users can reconnect almost immediately.
Advantages of Server Clusters
Despite their limitations, clusters can significantly improve system availability in case of hardware
or software failures or during planned maintenance.
IMPORTANT To take advantage of four-node clustering and 64GB memory support, you must
install Windows 2000 Datacenter Server.
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The advantages of
clustered Windows 2000 systems are:
Cluster Hardware Configuration
A shared Small Computer System Interface (SCSI) bus and two network cards are required in
addition to typical server equipment, such as a local disk where the operating system must be
installed.
The private network adapter is not a requirement, but it is necessary if you want to create a
cluster with complete hardware redundancy.
The nodes in a cluster are connected by up to three physical connections:
Shared Storage bus. Connects all nodes to the disks (or RAID storage systems) where all
clustered data must reside.
Public network connection. Connects client computers to the nodes in the cluster.
Private network Connection. Connects the nodes in a cluster and ensures that the nodes
will be able to communicate with each other in the event of an outage of the public local
area network (LAN). The private LAN is optional but highly recommended. Low-cost
Ethernet cards are sufficient to accommodate the minimal traffic of the cluster communication.
TIP It is advisable to purchase complete cluster sets from reliable hardware vendors instead
of configuring the cluster hardware manually.
NOTE: Only one node can gain access to a particular disk at any given time even through the
disks on the shared SCSI bus are physically connected to all cluster nodes.
Windows 2000 Clustering Architecture
To act as one unit, clustering Windows 2000 computers must cooperate with each other closely.
The Cluster service consists of several internal elements and relies on additional external
components to handle the required tasks.
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Resource Monitoring and Failover Initiation
The health of each cluster resource is monitored by the Resource Monitor, which is implemented
n a separate process communicating with the Cluster service via remote procedure calls (RPCs).
Joining a Cluster and Event Handling
When you start a server that is part of a cluster, Windows 2000 is booted as usual, mounting and
configuring local, noncluster resources. After all, each node in a Windows 2000 cluster is also a
Windows 2000 Advanced Server or Datacenter Server in itself.
From the point of view of other nodes in the cluster, a node may be in one of three states: offline,
online, or paused.
Lesson 2:
Load Planning and Failover Strategies
Microsoft Outlook 2000 and Exchange 2000 Server are designed to overcome these shortcomings
in a smart way. For example, you don’t need to restart Outlook 2000 to reconnect. A simple
switch to another folder in your mailbox (let’s say from Inbox to Contacts) does the job. Exchange
2000 Enterprise Server, again, supports multiple storage groups in the information store, which is
the basis of static load balancing in clustered Exchange 2000 Systems.
Load-Balancing Clusters
To best utilize the hardware resources available in a cluster, most organizations implement combined
application servers that provide more than one kind of client/server services to their users.
Active/Active Clustering
It may be desirable to dedicate individual clusters to one application type. For instance, you might
want to configure a two-mode cluster for Microsoft SQL 2000 Server and another four-node
luster for Exchange 2000 Server only. Keep in mind that each virtual server requires access to its
own disk resources, meaning one or more dedicated sets of physical disks.
NOTE: Exchange 2000 Enterprise Server supports active/active clustering.
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To maximize the use of all available server in a cluster while maintaining a failover solution, you can
configure multiple virtual servers and distribute them across your node. However, only one
resource group and therefore one virtual server can own a resource.
TIP: Theoretically, you can configure one virtual Exchange 2000 Server per physical disk, including
the disk containing the quorum resource. However, Microsoft does not recommend adding
Exchange 2000 Server services to the virtual server representing the cluster (that is, owning the
quorum disk). Defining dedicated virtual servers for Exchange 2000 simplifies service maintenance,
such as taking a virtual Exchange 2000 system offline.
Full Load with Hot Spare
When all nodes are online, Node D does not own a virtual Exchange 2000 server. This is the hot
spare assuming the role of an Exchange 2000 server in case another node in the cluster fails or is
unavailable for maintenance reasons. Provided that you don’t run other applications on the hot
spare, such as SQL 2000 Server, a single node failure will not affect the system performance.
Full-Load Active Nodes
The hot spare configuration bears the disadvantage of an idle server system when every node is
operational. If you don’t want to invest in this extra server, configure a three-node cluster with
our disks. The disadvantage of a full-load cluster is that users might experience performance
losses if one node has to take over the load of a failed member.
To avoid measurable performance losses, you would have to operate the nodes below the
following theoretical limits:
· Two-node clusters. 50% of the node’s power (which is a good as configurating
an active/passive cluster and using 100% of the active node’s power.
· Three-node Clusters. 66% of the node’s power.
· Four-node Clusters. 75% of the node’s power.
However, in most cases it will be acceptable to operate the nodes of a full-load cluster at their
maximum capabilities because node failures or failures due to maintenance should seldom occur
and temporary performance losses are usually not critical. Note that central processing unit
(CPU) utilization is not a perfect measure of the node’s power; a node will begin to experience
performance degradation if operating above 70% peak CPU utilization for an extended period
of time.
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Exchange 2000 and Virtual Server Limitations
Several Exchange 2000 Server components are not supported in a cluster, and others can only
run in an active/passive configuration. The Message Transfer Agent (MTA), for instance, cannot
run on more than one node in the cluster, implicitly enforcing an active/passive configuration. The
same restriction applies to the Chat Service.
The Exchange 2000 components supports the following cluster configuration:
· Chat. Active/passive
· Full-Text indexing. Active/Active.
· HTTP. Active/Active.
· IMAP. Active/Active.
· Information Store. Active/Active
· Instant Messaging. Not supported.
· Key Management Service (KMS). Not supported.
· MTA. Active/passive
· Network News Transfer Protocol (NNTP). Not supported.
· POP3. Active/Active.
· Simple Mail Transfer Protocol (SMTP). Active/Active
· System Attendant (SA). Active/active.
Important: Exchange 2000 Server supports only one public store in a cluster. When adding an
additional virtual server, make sure you delete the public store in the new resource group before
bringing the virtual server online.
Failover and Failback Procedures
Failover and failback are cluster-specific procedures to move resource groups (with all their
associated resources) between nodes.
Failover
A failover can occur in two situations: Either you trigger it manually for maintenance reasons or
the Cluster Service initiates it automatically in case of a resource failure on the node owning the
resource.
The Failover Manager is now responsible for deciding where to move the resource group. It
communicates with its counterparts on the remaining active nodes to arbitrate the ownership
of the resource group. This arbitration relies on the node preference list that you can specify
when creating resources in Cluster Administrator.
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Failback
If you have specified a preferred owner for a resource group, and this node comes back online
again, the Failover Manager will fail back the resource group to the recovered or restarted node.
By Default, resource groups are set not to fail back automatically when the original node is recovered.
Without manual configuration of a failback policy, groups continue to run on the alternate node after
the failed node comes back online.
Lesson 3:
Clustering Support in Exchange 2000 Server
Many Exchange 2000 Server components support active/active or at least active/passive clustering.
However, several components, such as the NNTP service, the KMS, or connectors to other mail
systems are not supported.
Exchange 2000 Server Clustering Installation
The installation of Exchange 2000 Server in a cluster is a process of four stages.
You need to install Windows 2000 Advanced Server or Datacenter Server on all nodes in the
cluster. You have to install the Cluster service on the nodes and configure the cluster environment.
Exchange Server installation. Exchange 2000 Server must be installed on all nodes with exactly
the same parameters, and, after that, you can configure and start virtual servers in Cluster Administrator.
IMPORTANT: You cannot install Exchange 2000 Server on a nonclustered server and integrate
this installation into a cluster afterward. Furthermore, it is a good idea to test the installation in a
cluster prior to deploying Exchange 2000 Server in the production environment. Exchange 2000
Server may not function properly with your hardware. You need to ensure that a dedicated
Physical Disk resource is available for Exchange 2000 Server.
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Installing Exchange 2000 in a Cluster
It is easy to install Exchange 2000 Server in a clustered system. Setup then copies and configures
the Exchange 2000 components and resource DLLs and sets the Exchange 2000 service to start
manually.
IMPORTANT Do not start or stop clustered Exchange 2000 services in the Services management
tool. You have to use Cluster Administrator to bring clustered services online or offline.
Clustered Installation Features and Dependencies
During installation of Exchange 2000 Server in a cluster, resource DLLs and other components are
added to the configuration of each node. It is important that you install only one node at a time
using the same account you used to install the Cluster service.
During installation, you need to place the binary files on the local system drive of each node. The
binary files are not shared between the nodes. Don’t forget to make sure that drive M is not in
use on any node because when you configure virtual servers later on, the Microsoft Web Storage
System will use the M drive by default.
Setup Initialization File
Because you must install the same Exchange 2000 components on all the nodes of the cluster, it is
a good idea to create and use a SETUP.INI file.
Exercise Summary:
Installation of Exchange 2000 Server is straightforward process. Setup detects that it is started on
a cluster node and configures the Exchange 2000 components and services appropriately. The
Exchange 2000 services will be configured to start manually. Don’t start the services in a cluster
in the Services Management tool because this undermines the cluster environment. Clustered
services are managed within Cluster Administrator.
IMPORTANT Do not configure restart settings in the Services management utility for services
that have been installed in a cluster; it would interfere with the cluster management software.
Resource Groups and Virtual Servers
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As soon as you have installed Exchange 2000 Server on all cluster nodes, you are ready to
configure resource groups. Each virtual server (equivalent to a resource group) requires an IP
address and a network name.
Each virtual Exchange 2000 server requires one or more shared disk resources where the
Information Store databases must be placed.
Exercise Summary:
You can configure and maintain Exchange 2000 resources in a cluster through Cluster
Administrator. Separate physical hard disks are required for each virtual server, as well as a
unique IP address and a network name.
IMPORTANT Each resource group in a cluster running Exchange 2000 Server must contain
an IP address, network name, disk, and the Exchange SA resource. Other resources, such as
automatically created protocol virtual servers, may be removed.
Configuring Additional Virtual Servers
Depending on your load-balancing and failover strategy, you might want to configure multiple
virtual Exchange 2000 server in a cluster. Each virtual server will appear in the network as a
separate server.
Public Information Store Dependencies
When configuring additional virtual servers, keep in mind that you cannot configure more than
one public store on the cluster. After adding additional virtual servers, you must delete the public
tore in new groups before bringing the resource groups online.
Virtual Protocol Servers
As soon as you have configured a virtual Exchange 2000 server, you can use the Exchange
System Manager to configure additional servers for Internet access protocols. (see page 241
bottom for the steps).
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Full-Text Indexing and Virtual Servers
Exchange 2000 Server supports full-text indexing in active/active cluster configurations.
Consequently, the Exchange MS Search Instance resource is added to your virtual server(s)
when you add the Exchange SA resource to your resource group. Even if you don’t plan to
use the full-text indexing feature of Exchange 2000 Server, do not delete the Exchange MS
Search Instance from your virtual server.
To enable full-text indexing on a cluster with the Exchange System manager, right-click the
desired store, and, from the shortcut menu, select Create Full-Text Index.
Exercise Summary:
Using Cluster Administrator, you can test the failover procedure for Exchange 2000 resource
easily. Just right-click on an Exchange 2000 resource, and select Initiate Failure.
All resources in the cluster group will be taken offline and then brought back online on another
available node in the cluster.
The process of stopping and starting instances is performed automatically and takes only
seconds.
Upgrading Exchange Server 5.5 Clusters
A direct update of an Exchange Server 5.5 cluster to Exchange 2000 Server is not possible.
However, you can install Exchange 2000 Server in an existing site and use the move-mailbox
Direct Cluster Update
Another option is to directly upgrade the existing information store database currently used in
the Exchange Server 5.5 cluster, provided that the cluster itself is running Windows 2000 with
Service Pack 1.
The file used is PRIV.EDB and it is stored in \Program Files\Exchsrvr\MDBData
directory.
Direct Upgrade Limitations
The direct upgrade approach requires you to install Exchange 2000 Server in the site of the
former Exchange Server 5.5
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Chapter Summary:
network name, and disk resources.
cluster can contain multiple virtual servers.
concurrent access to physical disks from more than one node.
over from the failed node to another node in the cluster, but it is impossible to activate
the same virtual server on more than one node at the same time.
installed and properly configured first. Each node must be rebooted to complete the
installation of the node.