Differences between migration and upgrade

There are three options for deploying a new Windows Server 2008 R2 operating system:

•    In-place upgrade
•   Clean install
•    Migration

In-place upgrade and clean install both have advantages and disadvantages. This guide describes the third option: migration.

There is a difference between migration and an in-place upgrade. Migration is required when hardware differences do not permit an upgrade. Because Windows Server 2008 R2 is an x64-only-based operating system, it is impossible to upgrade x86-based versions of Windows Server 2003 or Windows Server 2008 to a computer running Windows Server 2008 R2.

In addition, server migration can be a preferred deployment mechanism in a number of other scenarios:

• ·         When the performance of the old server has degraded as a result of numerous software installations, updates, and patches
• ·         When a physical server must be migrated to a virtual server
• ·         When your scenario calls for migration from a full installation option to a Server Core installation option

You can use the instructions in this guide to migrate legacy settings and data to the new operating system.

NOTE: If your existing hardware is x64-based but it is running an x86-based operating system, you must still use the instructions in this guide to migrate your server roles.

Upgrade and migration methods

Method	Advantage	Disadvantage
In-place upgrade (not discussed in this guide)	All your current settings and configurations are retained.	The upgraded server retains all the old data. In-place upgrade requires more downtime because the existing operating system is being replaced with the new operating system. If the in-place upgrade is not successful, roll-back is more complex.
Clean install (not discussed in this guide)	Removes all the old data and configuration that you no longer need.	You must reconfigure the new computer.
Migration (discussed in this guide)	All your current settings and configuration are retained, while all the old data and configuration that you no longer need are removed. Provides a transition path from a physical environment to a virtualized environment and from a full installation to a Server Core installation. Requires less downtime because the old server remains operational for the most of the migration process.	More planning and verification are required to ensure a successful migration.

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