Hosted Database Availability Group (DAG)
With the introduction of Database Availability Groups in Exchange 2010 and the improvements made in Exchange 2013, protection and high availability of Exchange Mailbox data has been made easy to setup and manage, with no previous knowledge of clustering required to get it working.
How it works
Our hosted database availability group (DAG) solution works by extending this protection to the cloud. The solution works by placing a Exchange server on our secure cloud and keeping a passive copy of your mailbox data offsite, that can be used to mount the mailboxes in the event that anything should happen to the active primary copy. All this over a secure VPN tunnel and private network dedicated to your environment
Licensing during normal operation
During normal operation, the mailboxes and mailbox databases will be mounted and active on your on premise Exchange server. Because of this, there are zero user licensing costs associated with hosting a copy of you mailbox data in the cloud.
Licensing during DAG failover to the Cloud
Should the requirement be that than you need to activate your mailbox copy in the cloud for any reason, each user who has a mailbox on the cloud during this time will require a SAL (subscriber access license) under the SPLA guidelines. These charges will only ever apply on a rolling monthly basis. As soon as you fail back the databases to your production Exchange server the charges will cease.
For SPLA licensing costs please see our licensing section located here.