GDR concepts

The GDR solution provides a highly available environment by identifying a set of resources that are required for processing the virtual machines in a server during disaster situations.

The GDR solution uses the following subsystems:

Controller system (KSYS)
Site
Host
Virtual machines (VMs) or logical partitions (LPARs)
Storage
Network
Hardware Management Console (HMC)
Virtual I/O Server (VIOS)

The following figure shows the GDR architecture:

Figure 1. Components of GDR solution

Controller system (KSYS)
The controlling system, also called KSYS, is a fundamental component in the Geographically Dispersed Resiliency for Power Systems™ (GDR) solution. It provides a single point of control for the entire environment managed by the GDR solution.
Hardware Management Console (HMC)
The controller system (KSYS) interacts with the HMC for processes that involve host, Virtual I/O Server (VIOS), and disk subsystem resources. These processes include discovery, monitoring, recovery, and cleanup.
Sites
Sites are logical names that represent your sites. You must create sites at the KSYS level. All the Hardware Management Consoles, hosts, VIOS, and storage devices are mapped to one of the sites.
Hosts
A host is a managed system in HMC that is primarily used to run the workloads. A host can also be called as a server or a Central Electronics Complex (CEC). Hosts are identified by its universal unique identifier (UUID) as tracked in the HMC.
Virtual machines
Virtual machines, also known as logical partitions (LPARs), are associated with specific Virtual I/O Server (VIOS) partitions for a virtualized storage to run a workload. A host can contain multiple virtual machines.
Virtual I/O Server (VIOS)
The KSYS receives information about the storage configuration of the virtual machines from VIOS.
Storage agents
A disaster recovery solution requires an organized storage management because storage is a vital entity in any data center. The GDR solution relies on data replication from the active site to the backup site.
Network
The network in your environment must already be configured for the existing resources that include hosts, HMCs, VIOS, and storage devices. The GDR solution requires that the KSYS node must be directly connected to the HMCs and the storage controllers in both the sites. The KSYS uses the HMC to interact with the hosts and VIOS, and the KSYS uses the storage controller to interact with the storage subsystem.