InfoWorld: Can you explain for us first the two typical approaches, which I believe are host-based software and storage-based data replication?
Smith: Yes. First is host-based software. In this case, software that runs on host environments and uses the host's network to copy data (and changes to the data) to another location. But host-based products must be separately deployed to each host -- a potentially daunting task. Host-based solutions consume host processing and network resources, potentially destabilizing an otherwise finely tuned application environment. And no single host-based product covers all of the application and operating system environments typically found in an IT infrastructure.
Second is storage-based data replication. In this case, software runs in storage subsystems and uses the storage processing capacity to copy data (and changes to the data) to another location. But storage-based products must be deployed separately to each storage environment. There is no coordination between data in different storage subsystems, even if applications require coherency of that data. Many storage system deployments require expensive edge devices to convert replicated data traffic from SAN transports to IP transports. Storage based products require matching storage at both production and disaster sites; you can’t use storage based replication between, say, an EMC disk subsystem and a HP disk subsystem. And storage-based deployments consume storage resources (such as disk access and cache memory), potentially impacting production workloads.
InfoWorld: Those are typical approaches, but you believe that another approach -- out-of-band replication -- may be a better option for some. Can you explain that?