Two upgrade approaches are available for upgrading from Microsoft Office SharePoint Server 2007 to Microsoft SharePoint Server 2010 which are
  1. In-place upgrade
  2. Database attach upgrade

In-place upgrade lets you move all the Microsoft SharePoint sites on the same hardware but the database approach lets you move your content to a new farm or desperate hardware. In addition, you may reduce downtime by merging up the In-place and database-attach upgrade.

An In-place upgrade enables you to install SharePoint Server 2010 on the same hardware, preserves your farm settings and makes customizations available after the upgrade. During the In-place upgrade, websites are available after the upgrade process whereas, in database attach upgrade, you will be allowed to upgrade content on a separate farm but you will not be able to upgrade any of the farm settings. You may upgrade multiple databases at the same time or upgrade them in any order that you want. This approach lets you combine several farms into a single farm. The database-attach approach is beneficial if you want to change your hardware or need to reconfigure your existing server farm topology during the upgrade process. With this approach, you detach the databases in your old farm and while you attach them to a new farm, the upgrade process runs and upgrades the entire database. This process is performed manually in a separate environment.

Plan your Upgrade Process

Database attach Upgrade

You can move to a new farm or hardware with database attach approach. You will detach all content databases from a current farm and attach them to a new server farm installation. While attaching the databases to a new farm, your upgrade process runs to upgrade the data in-place.

Hybrid Approach 1 for Read-only Databases

You can provide a read only access for the data to the users while you are attempting the upgrade process. Actually, the content databases in the original farm are set to read-only mode. Replicas of databases are also upgraded on the new farm.

Hybrid approach 2 for detach databases

Speed up your upgrade process by detaching and attaching databases to upgrade several databases at once with Hybrid approach 2. Although, it is an in place upgrade as you are upgrading the original farm but you can also use the other farm to carry out the upgrade and then attach the upgraded databases to the original farm. The original farm will not be able to serve requests during upgrade.

Summary:

Carrying out your upgrade with in place or database attach approach can be beneficial depending upon your business requirements. The In-place approach can be beneficial as it preserves all your farm settings with the SharePoint Server 2010 installation. You don't have to configure the farm settings manually. Your content databases will be upgraded sequentially. With the database attach approach, you need to set up a new environment to host your SharePoint 2010 Server. Once your new setup is up and running, the old environment will be made offline and all content databases will be moved to newer locations and upgraded at the same time. With the database attach upgrade approach, you will be successful in minimizing the down time as you will be upgrading several databases at once. Hybrid approaches including In-place upgrade with detached databases or database attach upgrade with read only databases help in decreasing the downtime of your environment and the end users will not experience a prolonged interruption of services.


Related Links:

SharePoint Migration || SharePoint Upgrade