Administrator Guide

Table Of Contents
NOTE: When you enable replication deduplication, the Storage Center creates a secondary 'Delta' volume. This secondary
volume adds to the overall volume memory usage and therefore will reduce the amount of configurable volume space
that can be deployed. The additional volume memory usage affects the overall System Scalability Guidelines that are
documented in the Storage Center Release Notes.
Replication Requirements
To replicate a volume from one Storage Center to another Storage Center, the requirements listed in the following table must
be met.
Requirement Description
Storage Center license The source and destination Storage Centers must be licensed for Remote Instant
Replay (Snapshot).
Unisphere Central configuration The source and destination storage system must be added to Unisphere Central
Data Collector.
NOTE: Replications cannot be created or managed when Unisphere is
connected directly to a Storage Center.
Storage Center communication The storage systems must be connected using Fibre Channel or iSCSI, and each
storage system must be defined on the other storage system.
Replication Bandwidth Control A Replication Bandwidth Control must be defined on the source Storage Center.
Replication Behavior When a Destination Volume Fails
When the destination volume becomes unavailable, each replication type behaves slightly differently. The replication types also
recover differently when the destination volume comes back online.
Scenario
Asynchronous Replication Synchronous Replication
Destination volume is
unavailable
Allows IO requests to the
source volume
High Consistency mode: Fails IO requests to the source
volume
High Availability mode: Allows IO requests to the source
volume
Destination volume comes
back online
Resumes transferring
snapshots from the source
volume and re-copies Active
Snapshot data (if enabled)
High Consistency mode: Resumes accepting IO requests
to the source volume
High Availability mode: Resumes transferring snapshots
from the source volume and copies the Active Snapshot
data that was missed while the destination volume was
unavailable
Replicating a Single Volume to Multiple Destinations
Multiple replications can be configured for a single source volume. Two topologies are supported:
Mixed mode: A source volume is replicated in parallel to multiple Storage Centers.
Example: Two replications are created in parallel:
Replication 1: Storage Center A Storage Center B
Replication 2: Storage Center A Storage Center C
Cascade mode: A source volume is replicated in series to multiple Storage Centers.
Example: Two replications are created in series:
Replication 1: Storage Center A Storage Center B
Replication 2: Storage Center B Storage Center C
Storage Center Replications and Live Volumes
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