## Master volume 

In most cases, the volume that contains a production copy of the data and that an application accesses. See also “Auxiliary volume” on page 796, and “Relationship” on page 810. 

## Metro Global Mirror 

Metro Mirror Global is a cascaded solution where Metro Mirror synchronously copies data to the target site. This Metro Mirror target is the source volume for Global Mirror that asynchronously copies data to a third site. This solution has the potential to provide disaster recovery with no data loss at Global Mirror distances when the intermediate site does not participate in the disaster that occurs at the production site. 

## Metro Mirror 

Metro Mirror (MM) is a method of synchronous replication that maintains data consistency across multiple volumes within the system. Metro Mirror is generally used when the write latency that is caused by the distance between the source site and target site is acceptable to application performance. 

## Mirrored volume 

A mirrored volume is a single virtual volume that has two physical volume copies. The primary physical copy is known within the SVC as copy 0  and the secondary copy is known within the SVC as copy 1 . 

## Node 

An SVC node is a hardware entity that provides virtualization, cache, and copy services for the cluster. The SVC nodes are deployed in pairs that are called I/O Groups. One node in a clustered system is designated as the configuration node. 

## Node canister 

A node canister is a hardware unit that includes the node hardware, fabric and service interfaces, and serial-attached SCSI (SAS) expansion ports. Node canisters are specifically recognized on IBM Storwize products. In SVC, all these components are spread within the whole system chassis, so we usually do not consider node canisters in SVC, but just the node as a whole. 

## Node rescue 

The process by which a node that has no valid software installed on its hard disk drive can copy software from another node connected to the same Fibre Channel fabric. 

## NPIV 

N_Port ID Virtualization (NPIV) is a Fibre Channel feature whereby multiple Fibre Channel node port (N_Port) IDs can share a single physical N_Port. 

## Object Storage 

Object storage is a general term that refers to the entity in which Cloud Object Storage organizes, manages, and stores with units of storage, or just objects . 

