In Part 1 of my video blogcast series on High Availability in Exchange Server 2010, I introduced you to the concept of database mobility, and the features known as database availability groups (DAGs) and mailbox database copies.
Please download the video and watch it full-screen. Part 3 is just under 3 minutes. Click on the video thumbnail below to go to the video. There is a Download link where you can download the video (use Right-click, Save Target As...).
Enjoy...and stay tuned for Part 4, coming soon!