Upgrades to Exchange 2007 require you to think
Whichever strategy you use, you must be aware of any special roles, applications, and add-ons you are using that will not be compatible with Exchange 2007. Although you can allow these legacy servers to be part of the organization for a while, keeping legacy servers around indefinitely may create more problems than it
Under what circumstances should you add an Exchange server? How do you know whether you need an additional Active Directory global catalog server? When should you add mailbox servers to a remote Active Directory site? When should you create more storage groups? Or mailbox databases? How many mailboxes should be located on a single mailbox database?
These are all questions that affect your Exchange 2007 design, deployment, and even day-to-day operations. If you don't provide sufficient resources, then the Exchange organization will not
This a good topic to address in its own chapter so we can give you ideas and guidance on the factors that may affect your decision to scale upward and outward.
Topics in this chapter include the following:
Deciding when to grow
Performance monitoring basics
Adding more mailbox storage
Enabling local continuous replication
Do you have clear guidance that tells you when you should expand, add servers, or add capacity? Sometimes your gut instinct just
If you are lucky, you can back up your request for a new server or more capacity with tangible evidence. We will discuss both the
When you are trying to increase your budget, nothing impresses your boss more than having hard
The first factors we'll discuss actually involve organizational requirements. A number of different
Clustering always requires at least two servers; one server is the active mailbox server and one server is the passive server. This includes shared copy clusters as well as clustered continuous replication clusters.
Other server roles cannot be installed on a clustered mailbox server. This means that other roles, such as Hub Transport, Client Access, or Unified Messaging servers, must be placed on a separate physical machine.
Fault tolerance for internal message routing is achieved with multiple Hub Transport servers. Exchange 2007 will automatically load-balance between multiple Hub Transport servers in the same Active Directory site.
Fault tolerance or higher availability for server roles such as Client Access or Unified Messaging is achieved with multiple servers and using a load-balancing technology (recommended) or DNS round
Each Active Directory site that contains a Mailbox server must have the Hub Transport and Client Access server roles. If the Unified Messaging server role is used, the Active Directory site must have a Unified Messaging server installed in the site.
Using Edge Transport services always requires an additional Windows server. Providing fault tolerance for Edge Transport server roles means installing at least two Edge Transport server roles. It is recommended that the Edge Transport servers be installed in your organization's perimeter or DMZ network.
Large organizations will often create a dedicated Active Directory site containing domain controllers and global catalogs servers. These servers are then used exclusively by Exchange servers. This way Exchange does not interfere with domain controllers that are handling
Let's not forget about supporting network infrastructure services. In a small organization, a single Windows domain controller/global catalog server/DNS server will be sufficient. However, if your organization is supporting more than a few hundred mailboxes, then the requirements for more supporting infrastructure components will increase as well. Here are some factors that may increase the number of network infrastructure services your organization requires:
Some organizations split their DNS servers on to servers or appliances that are separate from the servers that support Active Directory. While we normally recommend using the Windows 2003 DNS server running on a domain controller, if you choose to move DNS to another system, make sure that you have redundancy and that all Windows servers are configured with a primary and secondary DNS server. If you want to use the Active Directory-integrated DNS zone feature of the Windows 2003 DNS server, then the DNS server must be running on a domain controller.
The generic recommendation for the number of domain controllers and global catalog servers is one domain controller CPU for each four Exchange CPUs. This does not take into consideration fault tolerance for the domain controllers, so in organizations with more than 500 mailboxes, we recommend at least one redundant domain controller. That domain controller should be configured as a global catalog server.
If fault tolerance is specified in your Exchange design, it should be specified in your Active Directory design. This means each Active Directory site that contains an Exchange mailbox server (and consequently Hub Transport and Client Access server roles) should contain two domain controller/global catalog servers.
Remember that Outlook 2000 and later
Another factor that we consider a tangible factor when designing an Exchange 2007 system is recoverability and meeting service level agreements. As you will learn in Chapter 16, "Backup and Disaster Recovery," there are many types of outages and many approaches to recovering from them. Your Active Directory and Exchange designs may be subject to meeting a specific service level agreement that includes a statement defining recovery time for different types of outages:
The simpler a server's configuration is, the more quickly you can rebuild it if you have to perform a bare metal restore. Bare metal
The local continuous replication (LCR) feature of Exchange 2007 is one of its most
The time it takes to restore a mailbox database from backup is directly proportional to the
Potential speed of data restoration may affect the sizing of your servers. Calculate the amount of data that you will be hosting on any given mailbox server and then calculate how long it will take you to restore that data in a worst-case scenario. Is that acceptable in your environment?
Do you remember those hard numbers and graphs that
Performance monitoring may indicate insufficient hardware resources such as memory or disk I/O capacity on existing servers.
When querying a domain controller or global catalog, performance monitoring may pin-point bottlenecks that indicate either a performance problem or an overloaded domain controller/global catalog.
The final tangible factor in sizing servers and choosing hardware is the
Satellite or regional offices require their own Exchange server hardware even in the face of consolidation.
Executives or some divisions of an organization expect to be on isolated server hardware.
A department feels like having their mail on a server with everyone else is not secure enough.