SharePoint content has historically been stored in an SQL database, and this hasn’t changed in SharePoint 2010 deployments. In fact, the number of databases created in a SharePoint Server 2010 deployment has grown significantly to include new databases for logging, search, and the new managed metadata taxonomy store.
As in SharePoint 2007, each site collection created in SharePoint 2010 can have its own dedicated content database, making it easier for backup and redundancy.
The recommended size for a SharePoint 2010 site collection database is no greater than 200GB where there is only one site collection occupying the database. The recommended size is 100GB where there is more than one site collection occupying the ...