How to Rebuild Your Exchange Organization

A new wizard makes moving existing Exchange Server machines less difficult

No one is right all the time, not even highly paid external consultants who plan Exchange deployments. However, Exchange consultants need to get adeployment's organization design right the first time they plan it. Organization design is a major part of an Exchange project. The Exchange organization establishes how all of a deployment's servers communicate with one another. Deployment designers spend hours deciding how to group servers into sites, how to use different types of connectors to link sites, and how to build a corporate Directory that Exchange Server synchronizes among sites. After planners implement an organization design, making changes to fundamental parts of the organization becomes prohibitively difficult. For example, until recently changing the name of an organization required you to reinstall Exchange Server on all the organization's servers.

This difficulty of changing an organization creates problems even whenorganization planners make no mistakes. Administrators of networks withappropriate designs sometimes need to integrate two sites­for example, when they upgrade the bandwidth of intersite connections. Network availability, in terms of speed and quality, is an enormous influence on site design. I recommend connecting servers to form a site only when you can provide at least 128Kbps of bandwidth between all the servers. However, the fewer sites you have in an organization, the easier the organization generally is to administer. So if bandwidth between two existing sites increases, administrators might want to combine the sites.

Business developments can also impose stress on a messaging system.Consider the position of messaging administrators when their company acquiresanother company. Both companies might use Exchange Server, but they'reunlikely to use the same name for their organizations. Merging multiplesites takes a huge amount of coordinated effort from all administratorsinvolved, and such a merger can grind an internal messaging system to a halt.

Technology improves, business arrangements change, and network plannersmake mistakes. Expecting Exchange to be flexible enough to accommodate changeseems reasonable. Microsoft has finally provided a tool to help you migrateservers from existing sites and merge Exchange sites. Microsoft's release of theExchange Move Server Wizard (formerly code-named Pilgrim) makes rebuilding an Exchange organization more feasible than the task was previously.Moving servers from one organization to another still requires a lot ofplanning, but the wizard is the tool you need to perform the brainsurgery.

Why Is Moving Servers Complicated?
Comparing the intersite migration of Exchange Server machines to brainsurgery might seem extreme, but integrating two large Exchange sites requires agreat deal of effort and attention to detail. To understand how complex theprocess is, think about how the Directory names objects.

The Directory allocates a unique distinguished name to all objects--­includingservers and mailboxes--­within the Directory. Exchange ensures each objectname's uniqueness by using the organization name as the root, so objects inherittheir organization and site names as part of their distinguished name. Everyobject in the Directory has a root of

/o=/ou=

Any change at an organizational or site level (such as moving a server fromone site to another) requires you to change the distinguished name for everyobject associated with the move. You can't just drag a server from one site toanother.

Examine the distinguished name of my server DBO-EXCHANGEIST, which Screen 1shows. To view this information, I started Exchange Administrator in raw mode byappending the /r switch to admin.exe. I selected DBO-EXCHANGEIST andselected File, Raw Properties. The Obj-Dist-Name property contains thedistinguished name. In Screen 1, Obj-Dist-Name is

/o=Digital Equipment Corporation/ou=Dublin/cn=Configuration/cn=Servers/cn=DBO-EXCHANGEIST

This distinguished name tells me that this server is in the Dublin site inthe Digital Equipment Corporation Exchange organization.

To move this server to another site in the same organization, I wouldhave to change the /ou=Dublin part of the distinguished name of all theobjects that Exchange associates with the server, including mailboxes, publicfolders, and distribution lists. I would need to adjust the Directory'sorganizational information about the source and target sites so the source siteknows that the server left it and the target site knows that the server joinedit. This move would also affect the contents of the Information Store (IS)because Exchange Server stores message recipients' distinguished names alongsidemailbox data. Finally, if I use intersite replication, I would need to make sureExchange Server replicated all my changes to all the other servers in theorganization.

A Wizard Appears
Microsoft knew for a long time that it needed to produce a tool for movingservers, and recent high-profile mergers of companies that use Exchange Serveradded fuel to the fire. Compaq and Digital both use Exchange Server, andthe companies have a total of more than 400 Exchange Server systems worldwide.Imagine merging 400 servers into one organization if the task involved manuallychanging the name of every object in one of the organizations.

The Move Server Wizard was originally part of Exchange Server 5.5 ServicePack 1 (SP1), but Microsoft removed the wizard from SP1 at the last minute toiron out a few bugs. The Move Server Wizard is now available for downloading athttp://backoffice.microsoft.com/downtrial/moreinfo/ex55sp1wizard.asp.

The wizard helps administrators perform four functions. The rename functionlets you move a server from a one-server site to form a new site. The splitfunction lets you move a server from a multiserver site to form a new site. Themove function lets you move a server from a multiserver site to another site.When you merge two sites, you use the move function to move all the site'sservers that don't host message or directory replication connectors. Then, youuse the merge function to move the site's last server, which hosts thesite's connectors, to the other site.

Microsoft deliberately chose these terms to identify the type of operationeach function offers. Forming a new site and joining an existing site arefundamentally different operations. When you form a new site, the site inheritsits configuration data and schema directly from the server that you've renamedor split off from an existing site. When a server moves into an existing site,the server inherits that site's configuration. For example, a server that movesinto an existing site picks up the site's email addressing defaults, andExchange Server generates new email addresses for all the server's mailboxes.When a server forms a new site, its mailboxes keep their existing addresses.

Preparing Servers for the Move
Before you can use the Move Server Wizard to rename, split, or move a serveror merge sites, the servers you're planning to move must run Exchange Server 5.5SP1. SP1 makes several changes to the IS that support moving a server and takesadvantage of an Exchange Server 5.5 update to the Message Transfer Agent(MTA) that allows redirection of mail to a moved server. Exchange Serveraccomplishes MTA redirection through a new address type that Microsoft callsX.500. (These addresses have no connection with the international X.500standard; Microsoft uses the address type only to differentiate the wizard'saddresses from the addresses of day-to-day messaging operations.) A server'sX.500 addresses hold the old internal addresses for mailboxes you move with aserver. After users' mailboxes move, you can reply to messages the users sentbefore the move as if the users' addresses hadn't changed. Your replies willcontain the users' old addresses. When the MTA receives your replies, it usesthe X.500 addresses to resolve the old and new addresses, then sends the replyto the server's new location. When you move a server into an existing site, theserver in the destination site that you tell the wizard to query forconfiguration information about the site must also run Exchange Server 5.5 SP1.The other servers in the site can run Exchange Server 5.5 or Exchange Server5.0.

Generally speaking, the Move Server Wizard can move only server-specificdata. You must review everything that a server shares (or potentially shares)with other servers before the move, and move those items manually. Items thatservers can share include public folder replicas (including a replica of thesite's Offline Address Book), messaging connectors, directory replicationconnectors, the Key Management Server (KMS), and Outlook Web Access (OWA). Themost important items that you need to manually move are public folder replicasand messaging and directory replication connectors. Not many servers run KMSbecause few organizations implement Exchange Server's advanced securityfeatures. More servers host OWA than KMS, but moving OWA is straightforward; itrequires only reconfiguring the software after the server moves to its new site.

Moving public folders and connectors requires more care and time. First,you must identify the set of public folder replicas on the system you'replanning to move. Use Exchange Administrator to examine the properties of thePublic IS and retrieve a list of public folders. Then, select each folder andremove the replica from the server you're moving. If the replica is theonly instance of the folder in your server's site, you need to arrange foranother server in the site to hold a new instance of the public folder ifyou want the site to retain a replica of the folder. If a remote site that haslimited administrative access to your server's site owns the public folder inquestion (this capability is a new feature in Exchange Server 5.5), you must askthe administrator of the owning site to create the new instance. After you haveremoved all the public folder replicas from your server and created newinstances on other servers, wait about a day before moving the server to ensurethat Exchange Server has replicated your new public folder replica list to theother servers in the organization.

Moving connectors requires coordination across multiple sites. In thesimplest scenario, the server you want to move is a target for a remote siteconnector. In this case, you merely remove the server's name from the list oftarget servers in the sites on both sides of the connector. Moving a bridgeheadserver is more difficult. X.400, Simple Mail Transfer Protocol (SMTP), anddirectory replication connectors operate on the bridgehead principle, by which abridgehead server hosts a connector on behalf of a site. If the server you wantto move serves as a bridgehead for any connectors, you must move the connectorsto another server. Exchange Server automatically announces bridgehead servers tothe sites on either side of the connection, so when you move the connector to another server, you must make sure to change the connector's configuration inthe same way on both sites. Let replication carry details of a connector'sconfiguration changes to all parts of the organization before you move theserver that originally held the connector.

Finally, when you work with the Move Server Wizard, make sure your server'sMTA queues don't contain messages waiting to go to other sites. A queue that hasmore than 100 messages is a danger signal. Investigate why the queue accumulatedthe messages and reduce its size before you proceed with moving your server.

Preparing Users for the Move
Moving a server affects users in several ways. The server is obviouslyunavailable to users during its move. In addition, you need to ask remote usersto connect to the server and send mail they have queued up before you commencethe move. After the server moves, all users who connect to the Exchange Servercomputer via a Messaging API (MAPI) client--­such as the Exchange client orOutlook--­must recreate their user profile before they can connect to theserver. (User profiles contain the distinguished name of the user's mailbox, soafter the server that holds the mailbox moves, the old profiles won't work.)

Users' offline stores hold slave replicas of folders on an Exchange Servercomputer; they synchronize their contents with the server folders you specifyand make those folders available for offline access. (For more information about offline stores, see "Exchange and Groupware," July 1997.) Remote userswho have an offline store must delete and recreate their offline store if youmove a server that hosts folders the offline store points to. The move affectsthe contents of the IS, so the offline store is no longer valid. You can't scanthrough an offline store and update its contents to match the IS; your onlyalternative after moving a server is to recreate all offline stores that includereplicas of folders on that server. Be aware that offline stores can be large.My offline store is larger than 250MB. Recreating large files takes time,especially across slow links.

Finally, if your organization uses advanced security, moving a serverinvalidates your current X.509 certificates. You need to issue new keys afterthe move, so before the move, your users must use their existing keys to decryptall encrypted messages. If users fail to decrypt their messages, you permanentlylose the contents of the encrypted messages.

The Wizard Begins
Immediately after the Move Server Wizard starts, it checks theserver's configuration. Screen 2, page 136, shows the first screen you see inthe wizard. Microsoft takes great care to outline the risks of attempting a movewithout proper preparation. I agree with all the warnings. Only fools rush tomove servers without good, detailed planning.

After you review Microsoft's warnings and click I Understand to expressthat you are prepared to proceed, the wizard checks the server's configuration.It carefully examines messaging connectors to ensure that moving the serverwon't affect message flow within the organization. If the wizard discovers thatthe target server connects its site to another site, you'll see a messagesimilar to the one Screen 3, page 136, shows.

If the wizard doesn't detect any connectors on the server you want to move,it prompts you to decide whether to move the server into an existing site orcreate a new site. This decision is the most fundamental choice you make in theprocess of moving a server. Screen 4 shows the dialog box in which you make thischoice. (This dialog box looks similar to the dialog box in which you decidewhether to create a new site or join an existing site when you first installExchange Server on a new server.)

Exchange Server associates every mailbox with a Windows NT user account. Ifyour server move also involves changes to your NT environment, you must accountfor those changes in your plan for moving the server. For example, suppose eachdepartment of your company operates a separate NT domain. If you want to move anExchange Server machine from one department to another, you need to update theserver's mailboxes to run under NT accounts in the new department's domain. Thewizard makes all the necessary changes to the Exchange Server Directory, but youneed to create the new NT accounts and inform users when their NT accounts andpasswords change.

Go or No Go?
After the Move Server Wizard finishes checking your environment, it displays a status report, as Screen 5, page 138, shows. At this point, you must decide whether to go ahead with the server move. The wizard hasn't yet made any changes to the Directory or IS, but the wizard's preparatory checks have confirmed thatit can move the server. You can run the wizard several times up to this point to confirm that everything's ready to go before you commit yourself to the move. The wizard displays a dialog box or error message for any problems it detects. These boxes let you make decisions (such as how to handle distribution lists) or tell you to perform certain tasks before proceeding.

Running the wizard to test move conditions is an excellent way to ensurethat you're ready to perform a move. You might want to run it a few days beforethe move just to make sure you don't need to perform any additional preparatorysteps. Preparing for a weekend move only to find at the last minute that amessaging connector at a remote site still points to the server you want to move is not pleasant.

After you click I Understand, the Move Server Wizard swings into action andbegins processing the move. Screen 6, page 138, shows the progress report that Exchange Server displays as the wizard proceeds. The wizard does all of its work on the server you're moving. This work doesn't affect any of the other servers in the organization until Exchange Server introduces the server into the target site when the Exchange services start after the move is complete.

The Wizard at Work
Behind the scenes of a server move, the wizard does a lot of work similar tothe processing that installing Exchange Server on a new server requires. In newinstallations, Exchange Server prompts you for the name of a new site or thename of a server in an existing site from which Exchange Server can fetchinformation about the site. Equipped with this information, the installationprocedure builds a Directory for the new Exchange Server system. When theinstallation procedure is complete and the Exchange services start, theDirectory holds enough information for the server to establish a new site orbegin intrasite replication with other servers in an existing site. Intrasitereplication completes the process of integrating a server into an existing site;through replication, Exchange Server populates the new server's Directory withdetails about the configuration of servers, connectors, mailboxes, and otherobjects in the site.

The Move Server Wizard must perform similar tasks, but it starts with afull Directory that contains objects' distinguished names, which must change forthe move to be successful. To change objects' distinguished names, the wizardcreates a temporary database at the beginning of the move process, thenpopulates that database with objects that must move and configuration data forthe target site. This configuration data includes details about other servers inthe site and the site's default addressing or protocol support. If the serverforms a new site, it inherits this configuration information from its old site.If the server joins an existing site, the wizard extracts the necessaryconfiguration data from a server in the target site and inserts that informationinto the temporary database.

Because the IS links mailbox data to users' distinguished names, the wizardalso needs to update the IS. Rebuilding an IS is a far more serious undertakingthan rebuilding the Directory. The IS is usually several orders of magnitudelarger than the Directory, and many installations don't have the disk spacenecessary to build a temporary IS to contain changes to mailbox data. For thisreason, the wizard makes the necessary changes to the server's IS rather thancreating a temporary database for changes. My tests of the wizard reveal thatservers make necessary changes to distinguished names in the IS at around 3GB to4GB per hour. This figure varies depending on the server's hardwareconfiguration.

When the wizard has verified that your server is ready to move, it shutsdown the Exchange services and tells Exchange Server to replace the old site'sDirectory with the temporary database. When the wizard restarts the Exchangeservices, the services use the contents of the new database as the server'sDirectory, and the server either forms a new site or joins the existing sitethat the new Directory describes. Intrasite Directory replication can take a fewhours because Exchange Server must completely synchronize the new server'sDirectory with the Directories of the site's other servers. Most servers in mytests synchronized in less than 2 hours, but the time synchronization takesdepends on the size of the Directory. The Directory my tests replicated was60MB; it contained information about 16 sites and approximately 17,000recipients. Smaller organizations' Directories will take less than 2 hours tosynchronize; larger organizations will take more time. Replicating the GlobalAddress List (GAL) appears to take the longest time. Compare the total number ofobjects that the GAL on the moved server reports with the total number ofobjects in the GAL on another server in the site to determine when replicationhas finished.

After the Wizard Finishes
When the wizard finishes, it displays a screen that contains instructionsdetailing the tasks that you must complete to finish the move, as Screen 7shows. Make sure the Exchange services restart successfully on your movedmachine, and use the Exchange Administrator to verify that the server is nowpart of the new site. Then back up the system. Review the Exchange Serverdocumentation or Help files before beginning your post-move tasks.

You can't move an Exchange Server system without breaking links betweenobjects that depend on the Directory. After the wizard completes its work andthe server is part of its new site, you need to apply the finishing touches toyour move and reestablish all the links that the wizard doesn't handle.Reinstall OWA on the moved server. Configure new replicas for all the publicfolders you want on the server. Reset permissions on public folders to let userson the moved server retain their access rights. Issue new advanced securitykeys. Update management utilities such as link and server monitors andreferences to the server in third-party system-management tools. Review thecontent of distribution lists to make sure that everyone who needs to be on eachlist is on the list. Check to see whether the move broke any directory links,such as links between a manager and the manager's subordinates, and repair anybroken links. Delete any duplicate address book views you find. (Duplicateaddress book views can occur when the source and target sites define the sameaddress book view. For more information about address book views, see "MicrosoftExchange Server 5.0 Smoothes the Rough Edges," April 1997.)

If you split off a server to form a new site, you must also createmessaging and directory replication connectors to link the new site to theremainder of the organization. Verify that your connectors work before you setup Directory and public folder replication for a new site. (For more informationabout establishing directory replication connectors, see "ExchangeDirectory Replication," November 1998.)

The final step in the process is to restart the MTA on the moved server.You might be tempted to get all the services up and running as soon as possibleafter the wizard finishes, but you'd be wise to wait a while. I like to waituntil intrasite replication is complete and the whole site stabilizes beforerestarting the MTA. Exchange Server uses the MTA only for sending messagesoutside the site, so waiting to restart the MTA doesn't affect intrasitereplication or users' ability to send messages. Waiting ensures that when theMTA comes back online, it is ready to accept incoming messages that the sendersaddressed to the server in its old site and redirect them to the valid addressesin the new site.

Be Paranoid!
Proceed carefully when you make changes of this magnitude to an Exchangeorganization. Before you start moving a server, make sure that the network is ingood health and no replication messages exist in MTA queues. Perform a fullbackup of the Directory and ISs on the server that you're going to move. As soonas the wizard moves a server to a new site, perform full backups of the movedserver and all the servers in the target site. The move applies a huge number ofchanges to the Directories on all the servers that the move affects, so be sureto protect yourself with backups. Nothing is worse than having to restartthe process if you're unlucky enough to face a catastrophic hardware failureafter you move servers to a new site.

The Move Server Wizard isn't perfect, but it takes some of the pain out of reorganizing an Exchange organization or site. Moving a server stillrequires a lot of work. The wizard does its best, but it's generic software thatcan't be aware of all the twists and turns that exist in the wildlydifferent implementations of Exchange Server around the world. Take the time toproperly plan your move, run the wizard a couple times to verify thateverything's ready before you start moving anything, and proceed with caution.And keep in mind that backups are your best friend. Always know how you can back out of a situation if you need to.