514 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
For more information about Volume Mirroring, see Chapter 11, “Advanced Copy Services” on 
page 435.
11.6  Remote Copy services
This section describes the Remote Copy services, which are a synchronous remote copy 
called Metro Mirror (MM), asynchronous remote copy called Global Mirror (GM), and Global 
Mirror with Change Volumes. Remote Copy in an IBM Spectrum Virtualize system is similar to 
Remote Copy in the IBM System Storage DS8000 family at a functional level, but the 
implementation differs.
IBM Spectrum Virtualize provides a single point of control when remote copy is enabled in 
your network (regardless of the disk subsystems that are used) if those disk subsystems are 
supported by the system.
The general application of remote copy services is to maintain two real-time synchronized 
copies of a volume. Often, the two copies are geographically dispersed between two IBM 
Spectrum Virtualize systems. However, it is possible to use MM or GM within a single system 
(within an I/O Group). If the master copy fails, you can enable an auxiliary copy for I/O 
operations.
A typical application of this function is to set up a dual-site solution that uses two Storwize 
V7000 or IBM SAN Volume Controller systems. The first site is considered the primary site or 
production site, and the second site is considered the backup site or failover site. The failover 
site is activated when a failure at the first site is detected.
11.6.1  IBM Storwize family and SAN Volume Controller system layers
An IBM Storwize family system can be in one of the two layers: the replication layer or the 
storage layer. The system layer affects how the system interacts with IBM SAN Volume 
Controller and other external Storwize family systems. The IBM SAN Volume Controller is 
always set to replication layer. This parameter cannot be changed.
In the storage layer, a Storwize family system has the following characteristics and 
requirements:
/SM590000The system can perform MM and GM replication with other storage-layer systems.
/SM590000The system can provide external storage for replication-layer systems.
/SM590000The system cannot use a storage-layer system as external storage.
In the replication layer, an SAN Volume Controller or a Storwize system has the following 
characteristics and requirements:
/SM590000The system can perform MM and GM replication with other replication-layer systems.
/SM590000The system cannot provide external storage for a replication-layer system.
/SM590000The system can use a storage-layer system as external storage.
Tips: Intracluster MM/GM uses more resources within the system when compared to an 
intercluster MM/GM relationship, where resource allocation is shared between the 
systems. Use intercluster MM/GM when possible. For mirroring Volumes in the same 
system, it is better to use Volume Mirroring or the FlashCopy feature.