Migrating from Legacy Exchange

This chapter is from the book

Learning Exchange Server 2003

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This chapter is from the book

This chapter is from the book 

Learning Exchange Server 2003

Learn More Buy

Exchange Migration Roadmap

You cannot do an in-place upgrade from Exchange 5.5 to Exchange 2003. This applies even if you run Exchange 5.5 on Windows 2000. All upgrades from Exchange 5.5 to Exchange 2003 involve setting up new Exchange 2003 servers and moving mailboxes and connectors to those servers.

A basic migration has three phases: upgrade the domain to Windows Server 2003 (or Windows 2000, if you want to use the older operating system), deploy new Exchange 2003 servers, and then decommission the legacy servers. Here are the high-level details for each phase. The remainder of the chapter describes the details for performing each stage.

Domain Upgrade

The roadmap for a typical single domain upgrade looks like this:

1. Upgrade the current PDC to Windows Server 2003. Use a leapfrog upgrade so that you have fresh hardware on the newly upgraded server. A leapfrog upgrade involves installing a new NT BDC, promoting it to PDC, and then upgrading it to Windows Server 2003. This puts the domain (and forest) at an Interim functional level, which enables certain replication features in Windows Server 2003 (such as replicating individual group members rather than the entire Member attribute) while retaining backward compatibility with NT domain controllers.

2. Install additional Windows Server 2003 domain controllers. Don't tempt fate by having fewer than three domain controllers in a domain. This lets you take one domain controller down for maintenance and still have two up and running. Make as many of those domain controllers into GC servers as possible.

3. Decommission all NT BDCs. This eliminates the need to support legacy LanMan replication.

4. Shift the domain and forest to Windows Server 2003 functional level. This enables you to create Universal Security Groups, a requirement in a multiple domain forest.

Exchange 2003 Server Deployment

In the second phase, you'll deploy Exchange Server 2003 alongside your legacy Exchange servers. The roadmap looks like this:

1. Install SP4 and the latest security patches on all Exchange 5.5 servers. The ADC requires that any legacy Exchange server that acts as a Connection Agreement endpoint runs Exchange 5.5 SP3 or higher. This gives it the ADC the ability to read and write the legacy directory service via LDAP.

2. Normalize mailboxes. You need to spend an afternoon, maybe a long afternoon, validating that you have a one-to-one match between each legacy Exchange mailbox and an Active Directory user. At the same time, verify that each mailbox owner actually exists in Active Directory. The ADC tools perform this check, but you don't want to wait until the middle of the deployment to find out that you have a problem. Download the NTDSNoMatch utility from Microsoft to help with this work. See Knowledge-Base article 274173 for download and configuration information.

3. Verify public folder permissions. Spend another long afternoon going through the permission list for each public folder to ensure that the recipients and distribution lists actually exist. This avoids having zombies on the permission lists; that is, distinguished names that do not point at a valid account in the legacy Exchange directory service. Exchange 2003 contains safeguards against problems caused by zombies, but you'll have more success in your deployment if you avoid the problem completely. The Pfadmin tool is great for doing this work. Microsoft Knowledge Base article 188629 discusses how to remove invalid permission entries using Pfadmin.

4. Install the ADC. This updates the Active Directory schema to include all changes required by Exchange Server 2003, so it takes some preparation on the Windows side. This chapter describes those preparations.

5. Configure Recipient and Public Folder connection agreements. A Connection Agreement (CA) defines a pathway between Active Directory and the legacy Exchange directory service. The ADC uses CAs to transfer mailbox information from legacy Exchange to mailbox-enabled users in Active Directory and to create Distribution groups and Contact objects in Active Directory that match the distribution lists and custom recipients in legacy Exchange.

6. Install the first Exchange 2003 server. This creates a Configuration connection agreement in the ADC that copies information about the legacy Exchange organization into Active Directory. This server also runs an instance of the Site Replication Service (SRS) so the Exchange 2003 server can replicate directly with legacy Exchange servers in its site.

7. Move Connection Agreement endpoints. An Exchange 2003 server running SRS can act as an endpoint for connection agreements. The ADC Connection Agreement Wizard initially assigns endpoints to legacy Exchange servers. You have to manually move the endpoints of Recipient and Public Folder CAs to an Exchange 2003 SRS server.

Legacy Exchange Server Decommissioning

The final phase includes moving all Exchange operations over to the new servers and removing the legacy servers from the organization. Here's the roadmap:

1. Move mailboxes. Now that you have a fully functional Exchange 2003 server, you can move mailboxes to it from the legacy Exchange servers in the same site. You might want to install additional Exchange 2003 servers if you need the additional storage capacity and horsepower, or you can install Exchange 2003 Enterprise Edition and create additional storage groups and mailbox stores. Exchange is still in Mixed mode, so you cannot move mailboxes directly between servers in different legacy sites, which correspond to Exchange 2003 Administrative Groups.

2. Move connectors. The legacy Exchange server probably hosts a variety of connectors, such as the Internet Mail Connector (IMC), Site connector, Directory Replication connector, and possibly additional connectors for X.400 or third-party e-mail systems. You'll need to create new connectors on the Exchange 2003 server and make sure that those connectors work satisfactorily before removing the legacy connectors. You'll need Enterprise Edition if you have an X.400 connector.

3. Decommission legacy servers. At this point, you no longer need the legacy Exchange servers in this particular site. Uninstall Exchange from the servers. This removes their objects from the organization both in the legacy Exchange directory service and from Active Directory.

4. Repeat for all other sites. During the time that you're upgrading the first Exchange site to Exchange 2003, you can start upgrading the other sites using the same steps. You'll wake up one morning and all the legacy Exchange servers will be gone. This stage invariably takes twice as long as you originally had in the schedule.

5. Shift to Exchange Native mode. This step involves removing the Site Replication Service from all Exchange 2003 servers then setting a flag in the organization that releases it from compatibility with legacy Exchange.

6. Celebration. Don't forget this very important final step. Your Mode Shift Party (MSP) does not necessarily need to feature the unconscious forms of grinning Exchange administrators draped over piles of empty pizza boxes outside the server room, but that's certainly a possibility.

Special Considerations

The basic roadmap I'm following assumes that you start with a single domain and all legacy Exchange servers. Just a few of the possible scenarios include the following:

• Legacy Exchange servers running in several NT domains

• Legacy Exchange servers running in a Windows 2000 forest

• Mix of legacy Exchange servers and Exchange 2000 servers running in a Windows 2000 forest

Here are the additional considerations you need to include in your planning for these more complex situations.

Multiple NT Domains

If you have multiple NT4 domains and you choose to consolidate them into a single, pristine Windows Server 2003 domain, then your Exchange 2003 deployment roadmap changes just a little.

In an in-place migration, your efforts focus on transferring recipient and configuration information from the legacy Exchange directory service to Active Directory via the ADC. In a domain migration, you must first concern yourself with migrating security principals (user accounts, servers and desktops, and groups) from the NT domain to the Active Directory domain. Then you can set up the ADC and start your Exchange 2003 deployment.

An Active Directory attribute called SIDHistory contains the SID from the legacy NT domain so that users retain access to NT domain resources, such as their legacy Exchange mailboxes. Always migrate accounts using a tool that populates SIDHistory. Microsoft provides a free tool called the Active Directory Migration Tool (ADMT v2) on the Windows Server 2003 CD. You can get additional features and reporting capabilities by using third-party tools such as Domain Migration Wizard from Aelita Software or NetIQ's Domain and Exchange Migration Administrator.

Don't use the ADC to populate Active Directory with user accounts from the NT domain. The ADC does not populate SIDHistory and does not migrate user passwords, two critical features of a migration tool such as ADMT. Once you've migrated user accounts into Active Directory, then you can use the ADC to transfer legacy Exchange mailbox information to the objects, in the same way you did for an in-place migration.

From there, the roadmap matches an in-place upgrade. You install Exchange 2003 servers, move mailboxes and public folders and connectors to the new servers, decommission the old servers, shift to Native mode, and celebrate.

Legacy Exchange in a Windows 2000 Forest

If you have already deployed Windows 2000 but you still run legacy Exchange, you have a somewhat easier deployment roadmap. You can run Exchange 2003 in a Windows 2000 forest, but without some of the features you might want. (The feature set is detailed later in the chapter.) You should strongly consider upgrading your forest to Windows Server 2003 prior to deploying Exchange 2003 to get all the new features.

In general, the upgrade consists of modifying the Windows 2000 schema by running a tool called Adprep, and then either upgrading your Windows 2000 domain controllers to Windows Server 2003, or introducing new Windows Server 2003 domain controllers and decommissioning the old domain controllers.

An upgrade leaves the domain functional level at its current state. For example, if the Windows 2000 domain were in Mixed mode, the Windows Server 2003 domain and forest would be set to Windows 2000 Mixed functional level. You'll need to shift to a Windows 2000 Native functional level to get the ability to create Universal Security Groups prior to deploying Exchange 2003.

Once you've completed the Windows Server 2003 upgrade, you can begin deploying Exchange 2003. I do not recommend doing both upgrades at the same time because this introduces too much complexity into the deployment plan, makes recoverability more problematical, and complicates troubleshooting.

Mix of Exchange 5.5 and Exchange 2000 Servers

Speaking of keeping things simple, you should avoid deploying Exchange 2003 in the midst of an Exchange 2000 deployment that involves an upgrade from Exchange 5.5. Microsoft refers to this as a TIPTOS deployment, derived from the chemical symbols of the code names for the three Exchange products: Titanium for Exchange 2003, Platinum for Exchange 2000, and Osmium for Exchange 5.5.

Imagine the Monday meetings where you discuss configuration changes in sites with servers that have one, two, or all three versions of Exchange, maybe running with different service packs and security patches. You would need to include multiple strategies for directory service replication and multiple strategies for message routing; and you would need to keep track of the eccentricities of each type of server with your mix of antivirus, antispam, and backup agents.

Now imagine diagnosing and fixing problems caused when those servers don't want to interoperate for some inexplicable reason.

Now imagine what your resume might look like after you explain to your boss for the hundredth time why the CIO didn't get her e-mail.