Overview for Geographically Dispersed Resiliency for Power Systems

Disaster recovery of applications and services is a key component to provide continuous business services. The Geographically Dispersed Resiliency for Power Systems™ (GDR) solution is a disaster recovery solution that is easy to deploy and provides automated operations to recover the production site. The GDR solution is based on the Geographically Dispersed Parallel Sysplex™ (GDPS®) offering concepts that optimizes the usage of resources. This solution does not require you to deploy the backup virtual machines (VMs) for disaster recovery. Thus, the GDR solution reduces the software license and administrative costs.

The following high availability (HA) and disaster recovery (DR) models are commonly used by customers:

Cluster-based technology
VM restart-based technology

Clustered HA and DR solutions typically deploy redundant hardware and software components to provide near real-time failover when one or more components fail. The VM restart-based HA and DR solution relies on an out-of-band monitoring and management component that restarts the virtual machines on other hardware when the host infrastructure fails. The GDR solution is based on the VM restart technology.

The following figure shows the conventional high-availability and disaster recovery solution that is based on the HA clustering model. The GDR solution does not use this model.

Figure 1. Cluster-based disaster recovery model

The following figure shows the disaster recovery solution that uses the VM restart-based technology. The GDR solution uses this model.

Figure 2. VM restart-based disaster recovery model

The high availability and disaster recovery model that uses the GDR solution.

The following table identifies the differences between the conventional cluster-based disaster recovery model and the GDR solution:

Table 1. Comparison between the cluster-based DR solution and the GDR solution
Parameters	Cluster-based disaster recovery model	VM restart disaster recovery model that is used by the GDR solution
Deployment method	Redundant hardware and software components are deployed in the beginning of implementation to provide near real-time failovers when some of the components fail.	With virtualization technology, many images of the operating system are deployed in a system. These virtual machines are deployed on physical hardware by the hypervisor that allocates and manages the CPU, memory, and I/O physical resources that are shared among the VMs.
Dependency	This solution relies on monitoring and heartbeat capabilities within the cluster to monitor the health of the cluster and take recovery action if a failure condition is detected.	This solution relies on an out-of-band monitoring software that works closely with the hypervisor to monitor the VM environment and to provide a disaster recovery mechanism for the VM environment.
Workload startup time	The workload startup time is faster because the virtual machines and the software stack are already available.	The VMs require additional time to restart in the backup environment.
Cluster administration required	Yes	No
Error coverage	Comprehensive. This solution monitors the entire cluster for any errors.	Limited. This solution monitors the servers and the virtual machines for errors.
Deployment simplicity	This solution must be set up in each VM.	Aggregated deployment at the site level.
Protected workload type	Critical workloads can be protected by using this solution.	Less critical workloads can be selected for protection by using this solution.
Software license and administrative costs	This solution costs more because redundant software and hardware are required to deploy this solution.	This solution costs less because of optimized usage of resources.

A disaster recovery implementation that uses a set of scripts and manual processes at a site level might take more time to recover and restore the services. The GDR solution automates the operations to recover your production site. This solution provides an easy deployment model that uses a controller system (KSYS) to monitor the entire virtual machine (VM) environment. This solution also provides flexible failover policies and storage replication management.

The following figure shows the architecture and the basic components that are used in the GDR solution:

Figure 3. An example of GDR solution architecture

The architecture and the basic components in the GDR solution.