Resilient devices are physical resources, represented by a configuration object, such as a device description, that are accessible from more than one node in a cluster.
In the event of an outage, the point of access for the resource
is switched to the first backup node in the cluster resource group recovery
domain. Independent disk pools, or independent ASPs are resilient devices
that can go offline or come online without impacting the rest of system storage.
Additionally you can use geographic mirroring which is a subfunction of cross-site
mirroring (XSM) which is part of i5/OS™ Option 41, High Available Switchable
Resources. Geographic mirroring is a function that keeps two identical copies
of an independent disk pool at two sites to provide high availability and
disaster recovery. The copy owned by the primary node is the production copy
and the copy owned by a backup node at the other site is the mirror copy.
User operations and applications access the independent disk pool on the primary
node, the node that owns the production copy. 
A resilient device cluster resource group can contain a list of switchable devices. Each device in the list identifies a switchable independent disk pool. The entire collection of devices are switched to the backup node when an outage occurs. Optionally, the devices can also be varied on as part of the switchover/failover process. There are limitations related to the physical configuration associated with the list of switchable devices. See Independent disk pools for more information about how to set up the appropriate configuration for an independent disk pool defined to be resilient.
A resilient device CRG is very similar to the other types of CRGs. One difference, the list of switchable devices, was mentioned above. Another difference is that the exit program is optional for a device CRG. If environment or data specific processing is needed, an exit program can be used for the CRG. See the Create Cluster Resource Group (QcstCreateClusterResourceGroup) API for additional information about this type of CRG.