Whats the DAG hangup?
A replacement for Exchange 2007’s separate local and remote replication features, DAGs help perform mailbox and database-level failover, consolidate multiple cluster services into a single management console, and automate failover operations. VMware’s HA works at the server level and when a physical node in an ESX cluster fails, it automatically restarts a virtual guest on another physical host. DAGs and VMware features that perform automated live migrations, such as the Distributed Resource Scheduler (DRS) feature could potentially conflict, said Matt Liebowitz, a solutions architect at Kraft & Kennedy Inc., a Manhattan-based Microsoft and VMware channel partner that services law firms. VMware’s vMotion requires at least a few moments of downtime before a guest machine goes live on a hew host and if a DAG service at the application level loses a “ping” while the guest is migrating, it could trigger an unnecessary application failover. “I’ve seen it happen [with DRS and DAGs] in a coup
