I have been getting number of emails regarding the number of databases possible on standard and enterprise version of 2010. Though everyone is clear with the fact that a standard version can have 5 and enterprise can have 100 databases, some get confused when DAG comes into play. To make it clear for my readers, you can use either standard or enterprise 2010 for DAG & it will work, provided that Windows operating system is an enterprise or datacenter edition.
Now, if you have DAG configured, you can have a maximum of 5 databases in a standard edition and that includes both active and passive copies. Similarly, the 100 databases for enterprise includes both active and passive.
In short, you CAN’T have the maximum number of allowed databases as active and still have passive database copies on a DAG server. This information has to be taken into account while configuring a 2010 DAG.