## Rebuild area 

Reserved capacity that is distributed across all drives in a redundant array of drives. If a drive in the array fails, the lost array data is systematically restored into the reserved capacity, returning redundancy to the array. The duration of the restoration process is minimized because all drive members simultaneously participate in restoring the data. See also “Distributed RAID or DRAID” on page 821. 

## Reclaimable (or reclaimed) capacity 

Reclaimable Data is the capacity that is no longer needed. Reclaimable capacity is created when data is overwritten and the new data is stored in a new location, when data is marked as unneeded by a host using the SCSI unmap command, or when a volume is deleted. 

## Redundant storage area network 

A redundant SAN is a SAN configuration in which there is no single point of failure (SPoF); therefore, data traffic continues no matter what component fails. Connectivity between the devices within the SAN is maintained (although possibly with degraded performance) when an error occurs. A redundant SAN design is normally achieved by splitting the SAN into two independent counterpart SANs (two SAN fabrics), so that if one path of the counterpart SAN is destroyed, the other counterpart SAN path keeps functioning. 

## Relationship 

In Metro Mirror or Global Mirror, the association between a master volume and an auxiliary volume. These volumes also have the attributes of a primary or secondary volume. See also “Auxiliary volume” on page 81 6, “Management node” on page 827, primary volume, secondary volume. 

## Reliability, availability, and serviceability 

Reliability, availability, and serviceability (RAS) are a combination of design methodologies, system policies, and intrinsic capabilities that, when taken together, balance improved hardware availability with the costs that are required to achieve it. 

Reliability is the degree to which the hardware remains free of faults. Availability is the ability of the system to continue operating despite predicted or experienced faults. Serviceability is how efficiently and nondisruptively broken hardware can be fixed. 

## Remote fabric 

The remote fabric is composed of SAN components (switches, cables, and so on) that connect the components (nodes, hosts, and switches) of the remote cluster together. Significant distances can exist between the components in the local cluster and those components in the remote cluster. 

## Remote Support Server and Client 

Remote Support Client is a software toolkit that resides in IBM Storwize V5000 and opens a secured tunnel to the Remote Support Server. Remote Support Server resides in the IBM network and collects key health check and troubleshooting informations required by IBM support personnel. 

## SAN Volume Controller 

The IBM SAN Volume Controller is an appliance that is designed for attachment to various host computer systems. The SAN Volume Controller performs block-level virtualization of disk storage. IBM Spectrum Virtualize is a software engine of SAN Volume Controller (and Storwize family) that performs block-level virtualization of disk storage. 

