Chapter 2   Migration Overview


This chapter provides an overview of the migration process. The sections in this chapter are:

• "Migration Prerequisites"

• "Migration Toolkit"

• "Migration Process"

• "Choosing a SIMS Message Store Migration Method"
  • "Off-line Message Store Migration"

  • "On-line Message Store Migration"

  • "Incremental Message Store Migration"

Migration Prerequisites

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These migration procedures and scenarios assume the following prerequisites:

• The system to be migrated from is a SIMS 4.0 or Netscape Messaging Server 4.x system.

• The LDAP directory used with the system is the Netscape Directory Server 4.12

• The Netscape Messaging Server system uses UIDs of the form <LocalPart> or <LocalPart>@<FQDM>. (See "Netscape Messaging Server 4.x Directory Namespace Limitations".)

Migration Toolkit

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The migration toolkit is required for the procedures described in this book. It consists of the following:

• Schema files which provide multi-schema support during migration.

• imsdirmig command which converts directory entries to use the iPlanet Messaging Server schema. This command will run on all iPlanet Messaging Server supported platforms.

• imsdaaci command which creates an LDIF file to support iPlanet Delegated Administrator for Messaging. This command will run on all iPlanet Messaging Server supported platforms.

Migration Process

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The migration method you choose will depend upon three parameters. These are:

• Whether you are migrating a system from SIMS or the Netscape Messaging Server.

• The complexity of the mail system (whether the system operates on a single-standalone system, or consists of numerous systems fulfilling different functions and acting in concert together).

• Tolerance of downtime (that is how long customers can go without sending or receiving mail).

Whatever method is selected, certain basic objectives and procedures will be the same. These are briefly describe below.

For Netscape Messaging Server migrations, reimplement customized plug-ins. Since the iPlanet Messaging Server does not support messaging plug-ins, plug-in functionality will need to be redesigned and recoded using features of the new MTA. The MTA has functions that handle the most common plug-in functions. See "Netscape Messaging Server 4.x MTA Regressions/Changes".

Upgrade the directory server to Netscape Directory Server 4.12. See "Upgrading SIMS/Netscape Messaging Server to Netscape Directory Server 4.12".

Enable multi-schema support in the directory server. During migration it may be necessary to support the iPlanet Messaging Server schema simultaneously with the SIMS or Netscape Messaging Server schema. This involves installing the new schema files for SIMS and the Netscape Messaging Server on the LDAP master server as well as on all its replicas. (See "Supporting a Multiple Schemas".)

For multi-server deployments, install a configuration server. A configuration server is an LDAP server containing iPlanet Messaging Server configuration data. Note that you can install the iPlanet Messaging Server into the existing Netscape Messaging Server configuration server after you have A) upgraded to the new schema, and B) created a new Admin Domain in the configuration server.

Install the iPlanet Messaging Server. After the new iPlanet Messaging Server is installed, configure it so that it obtains user/group entries from the pre-existing directory server. (See the iPlanet Messaging Server Installation Guide.)

Convert/move message store. For SIMS environments: convert the SIMS message store to the iPlanet Messaging Server message store. This may be done off-line, on-line, or in user batches incrementally. (Refer to "Choosing a SIMS Message Store Migration Method"). For Netscape Messaging Server environments: Message store migration is automatic and on-line once the system is pointed to the message store.

Upgrade user, group, and domain entries to use the iPlanet Messaging Server schema. Since the iPlanet Messaging Server components can deal with users and groups in a mixed schema, this migration can be done incrementally and without any service interruption. However, once the migration to the new schema is done, it is difficult to move a group or user back to a host running the old messaging server. A utility, imsdirmig, is used to migrate entries to use the new schema.

For Netscape Messaging Server migrations, modify the directory such that all user and mailing list entries are located under a domain node in the Organization Tree. This is necessary to support domains as well as the iPlanet Delegated Administrator for Messaging GUI tool and utilities. This is described in "Using Existing Directory Information Trees in the iPlanet Messaging Server".

Modify the system to support the iPlanet Delegated Administrator for Messaging. Create the Delegated Administrator Service Administrator entry and Delegated Administrator Service Admin Group entry. Add the appropriate ACIs.

Choosing a SIMS Message Store Migration Method

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There are three methods for migrating the SIMS message store to the iPlanet Messaging Server message store. These are Off-line Migration, On-line Migration, and Incremental Migration. The method you choose will depend on the size of your message store, your tolerance for downtime, and whether you are running POP or IMAP. This section describes each of these methods, the advantages and disadvantages of each, and system scenarios for each method. The actual step-by-step migration procedures are described in later sections.

Off-line Message Store Migration

Off-line message store migration involves shutting down SIMS, installing the iPlanet Messaging Server, backing up the old SIMS message store data, restoring/converting it to the iPlanet Messaging Server message store data, and bringing the iPlanet Messaging Server on-line.

Advantages of off-line message store migration:

• Simplest and most straight forward of migration methods.

• Easiest to revert back to SIMS if desired.

• Maintains the correct message arrival order.

• Shortest overall migration time.

Disadvantages of off-line message store migration:

• Requires the longest server downtime (no client access). The downtime is approximately 1-2 hours for each 20 Gigabytes of message store to migrate¹ plus 1-2 hours to upgrade LDAP entries (depending on the number of entries and whether or not the mail host name changes).

Scenarios for off-line message store migration:

• Single or multiple server systems with 20 GB message store, 50K users, using either POP or IMAP.

  Estimated Downtime: 2-3 hours.

• Single or multiple server system with 100 GB message store, 200K users, either POP or IMAP.

  Estimated Downtime: 7-12 hours.

For detailed information on off-line migration, refer to "Upgrading from a Single-Server SIMS System Using the Offline Message Store Migration Method" or "Migrating Backend SIMS Mail Store Servers to the iPlanet Messaging Server Using the Off-line Migration Method".

On-line Message Store Migration

On-line message store migration involves installing the iPlanet Messaging Server and activating it as the default server such that new messages are received in new message store. Afterwards, the SIMS message store is migrated to the newly installed server while that server remains active and on-line.

Advantages of on-line message store migration:

• Minimal downtime.

• Simple and straight forward migration method.

Disadvantages:

• Message store migration may create an incorrect arrival order in the message store queue. As older messages are migrated from SIMS, they will be added atop new messages received in the iPlanet Messaging Server. The order of newly received messages may be mixed with older messages.

• Message store migration is slower because of the need to turn on sync (2-4 GB/hour depending on hardware compared to 10-20GB/hour when migrating off-line).

• Users who log in may temporarily see an empty mailbox, until their old messages and folders are migrated. Old messages in IMAP mailboxes are unavailable during migration. New messages that come into iPlanet Messaging Server message store are available.

Scenarios for on-line message store migration:

• POP-only user community.

• Single or multiple server system with 20 GB message store, 50K users, either POP or IMAP where A) minimal downtime is important, B) misordering of new messages with old messages is not crucial and C) temporary disappearance of all messages in users mailbox is allowable. If IMAP, users will not be able to access their old email until after it is migrated. Estimated Migration Time: 5-10 hours.

• Single or multiple server system with 100 GB message store, 200K users, either POP or IMAP. Estimated Migration Time: 25-50 hours.

For detailed information on on-line migration, refer to "Upgrading from a Single-Server SIMS System Using the On-line Message Store Migration Method" and "Migrating Backend SIMS Mail Store Servers to the iPlanet Messaging Server Using the On-line Migration Method".

Incremental Message Store Migration

In this scenario, the iPlanet Messaging Server is installed a new machine and activated for migrated users, while SIMS remains on active on the existing machine for users not yet migrated. Batches of user mailboxes are incrementally migrated from the old SIMS system to the new iPlanet Messaging Server system.

The basic steps of incremental migration are as follows: the iPlanet Messaging Server is installed while SIMS remains active. A batch of users is temporarily disabled from using the mail system and migrated from SIMS to the iPlanet Messaging Server. The iPlanet Messaging Server is then activated as the mail host for the migrated users, while the SIMS system remains active for the unmigrated users. Batches of users are continually migrated from SIMS to the iPlanet Messaging Server. When all users are migrated, SIMS can be deactivated. Downtime is limited to the batch of users being migrated.

Advantages of incremental message store migration:

• Downtime limited to batch of users being migrated.

• Useful for migrating very large message stores with many users where downtime is not well-tolerated.

• Allows you to migrate small numbers of users to the new system, while other users can continue to use the SIMS system.

Disadvantages of using the incremental migration:

• Requires extra hardware.

• The process is more complex.

• Once users are migrated to the new system, it is difficult to return those migrated users back to SIMS system. We recommend practicing on a small number of users before doing a full-scale deployment.

Scenarios for incremental message store migration:

• 500GB message store, 500K users, IMAP system, minimum user downtime.

• Any system where you want to migrate users gradually instead of all at once.

Migration performance is comparable to on-line migration. For details, refer to"Upgrading from a Single-Server SIMS System Using the Incremental Message Store Migration Method" and "Migrating SIMS Message Store Servers to the iPlanet Messaging Server Using the Incremental Migration Method".