566 Implementing the IBM Storwize V5000 Gen2 with IBM Spectrum Virtualize V8.1
However, this process also means that the application is exposed to the latency and
bandwidth limitations (if any) of the communication link between the master and auxiliary
volumes. This process might lead to unacceptable application performance, particularly when
placed under peak load. Therefore, the use of traditional Fibre Channel Metro Mirror has
distance limitations that are based on your performance requirements. The IBM Spectrum
Virtualize does not support more than 300 km (186.4 miles).
10.7.6 Metro Mirror features
The IBM Spectrum Virtualize Metro Mirror function supports the following features:
Synchronous remote copy of volumes that are dispersed over metropolitan distances.
The Metro Mirror relationships between volume pairs, with each volume in a pair that is
managed by a Storwize system or IBM SAN Volume Controller system (requires V6.3.0 or
later).
Supports intracluster Metro Mirror where both volumes belong to the same system (and
I/O Group).
The IBM Spectrum Virtualize supports intercluster Metro Mirror where each volume
belongs to a separate system. You can configure a specific system for partnership with
another system. All intercluster Metro Mirror processing occurs between two IBM
Spectrum Virtualize systems that are configured in a partnership.
Intercluster and intracluster Metro Mirror can be used concurrently.
The IBM Storwize V5000 Gen2 system does not require that a control network or fabric is
installed to manage Metro Mirror. For intercluster Metro Mirror, the system maintains a
control link between two systems. This control link is used to control the state and
coordinate updates at either end. The control link is implemented on top of the same FC
fabric connection that the IBM Storwize V5000 Gen2 system uses for Metro Mirror I/O.
The IBM Spectrum Virtualize implements a configuration model that maintains the Metro
Mirror configuration and state through major events, such as failover, recovery, and
resynchronization, to minimize user configuration action through these events.
The IBM Spectrum Virtualize supports the resynchronization of changed data so that write
failures that occur on the master or auxiliary volumes do not require a complete
resynchronization of the relationship.
10.7.7 Metro Mirror attributes
The Metro Mirror function in IBM Spectrum Virtualize possesses the following attributes:
A partnership is created between two IBM Storwize V5000 Gen 2 systems or an IBM SAN
Volume Controller system and IBM Storwize V5000 Gen2 system operating in the
replication layer (for intercluster Metro Mirror).
A Metro Mirror relationship is created between two volumes of the same size.
To manage multiple Metro Mirror relationships as one entity, relationships can be made
part of a Metro Mirror Consistency Group, which ensures data consistency across multiple
Metro Mirror relationships and provides ease of management.
When a Metro Mirror relationship is started and when the background copy completes, the
relationship becomes consistent and synchronized.
After the relationship is synchronized, the auxiliary volume holds a copy of the production
data at the primary, which can be used for DR.
The auxiliary volume is in read-only mode when relationship is active.
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