A device cluster resource group (CRG) supports device resiliency in IBM® i high availability environments. A device CRG contains one or a list of independent auxiliary storage pools (IASPs) which are replicated or switched between systems. IASPs can only be switched or replicated between nodes in the recovery domain for the device CRG. Access to the entire list of IASPs in the device CRG is switched to the backup node when an outage, planned or unplanned, occurs. When creating the environment, you can either create a new IASP or use an existing one.
There are IBM PowerHA® SystemMirror® for i technologies available to switch or replicate the data in the IASPs. The switchable logical unit (LUN) technology switches access of one copy of the IASP from the primary to the backup server. With replication technologies such as geographic mirroring, Metro Mirror, or Global Mirror, data is mirrored from the IASP at the production site to another IASP at the backup site. Usually these sites are geographically separate from one another, providing disaster recovery protection. In these environments, the device CRG controls switching access between mirrored copies of the IASP. When the production site experiences an outage event, the device CRG switches access to the IASP to the backup site.