AIX > Administrator > High Availability

HACMP's New Long-Distance Data Replication and Failover Technology

Most IT managers know the fear. The datacenter is running smoothly and delivering business-critical applications when suddenly a natural disaster or catastrophic event strikes--perhaps a massive blackout or a hurricane--and the entire complex shuts down. The staff is unharmed, but the systems are out of commission and it'll be days before the datacenter--with all its critical applications and information--can be brought back online. This is a bad time to start thinking about what you could have done to prepare for such a disaster.

The Product

If your applications are running on IBM pSeries servers, what you could've done is configure the new Geographic Logical Volume Manager (GLVM) on IBM High Availability Cluster Multi-Processing/Extended Distance (HACMP/XD) to mirror (replicate) all your business-critical data to a remote site in real time and immediately re-start your applications automatically at that remote site for high availability (HA) of your critical business systems. HACMP has been IBM's premier HA solution for more than 12 years with more than 12,000 customers. The XD option provides several technologies to extend HACMP's failover capabilities to remote sites through remote data mirroring and automatic takeover of remote disks.

HACMP/XD GLVM is a new HA function that can mirror data across a standard IP network of potentially unlimited distance and provide automated failover and failback of applications using this replicated data. GLVM performs this remote replication of AIX logical volumes using AIX's native LVM functions for optimal performance and ease of configuration and maintenance.

The new HACMP/XD GLVM significantly improves IBM's pSeries XD disaster recovery (D/R) and business continuity solution, which helps position it for anticipated growth in geographic D/R.

The Function and How It Works

HACMP/XD GLVM integrates directly with AIX's LVM, extending it to support data replication at remote sites. Using this remote data replication, GLVM also extends HACMP's local HA function to support failover of applications and data to these remote sites.

The HACMP cluster consists of two nodes connected by a TCP/IP WAN: Node A is in the Tucson, Ariz., datacenter and Node B is in the St. Louis, Mo., datacenter. Node A is the primary node for an HACMP resource group containing a logical volume with two copies, one local (on Node A) and one remote (on Node B). To the LVM on Node A, both copies of the data appear local, but a pseudo-device called a Remote Physical Volume (RPV) actually represents the second copy. This RPV has two parts: a client operating on the local node and a server operating on the remote node. 

Andrew Naiberg is a product-marketing manager with IBM. Andrew can be reached at

Skip Russell is a senior software engineer with IBM. Skip can be reached at

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