Using addcontentdb is one way to upgrade your SharePoint 2007 content to SharePoint 2010. There are some things to consider when doing it. Addcontentdb is a stsadm command and it takes a lot of resources. I recommend having a lot of free space on your sql server’s hard drives when you run it. At least 5 times the size of the database (more is better) to allow for the log files and content database increase in size. Also, while you are running it the following two databases seem to be locked.
Sharepoint_config
Sharepoint_admincontent
This means you can’t be making changes to those databases (creating web applications, deploying solutions, etc.) while you are upgrading. I have had different experiences with the speed of the operation but it seems to be dependent on the number of site collections more than the size of the content. It can take hours if there are a lot of site collections (as in the case of My Sites for example).
Quick and dirty of how to do the upgrade via addcontentdb
1. User SQL Server (for 2007 site) to back up the content database you want to move over.
2. Copy the backup file to somewhere the SQL Server for the 2010 site can get to it.
3. Restore the backup to the 2010 site
4. Create a web application, but don’t create a top level site collection.
5. Run the stsadm command addcontentdb
stsadm –o addcontentdb –url <url of new web application> -databasename <name of restored database>
6. Wait patiently while the database is upgraded.
You will now have an upgraded content database that is accessible via the new web url. It will look exactly (hopefully) like the old site. The search settings will not be transferred so you will probably get a scope error if you had any special scopes set up. You can do the Visual Upgrade to individually convert the sites to the new look and feel of SharePoint 2010. You will still have to install the custom web parts and solution to the 2010 environment after the upgrade for them to work.