Administrator Guide

Figure 18. Centralized Replication
About Replication Space
Volume replication between partners requires space on both the primary group (the volume location) and the secondary group (the
replica location). These space requirements are classied in the following way:
• Local replication reserve
Each volume requires primary group space for use during replication and, optionally, for storing the failback snapshot.
• Delegated space
To provide space for storing replicas, the secondary group delegates space to the primary group. All primary group volumes that
you replicate to the secondary group share the delegated space.
Each volume is assigned a portion of delegated space, called the replica reserve. The replica reserve for a volume limits the
number of replicas you can keep. When replica reserve is consumed, the oldest replicas are deleted to free space for new
replicas.
To make sure replication operations complete and to keep the desired number of volume replicas, you must allocate sucient
replication space.
To determine the optimal amount of replication space, Dell recommends that you set up replication using the default space values,
monitor activity over some time period, analyze the space usage, and make adjustments. These precautions will help you keep the
desired number of replicas while using replication space eciently.
About Local Replication Reserve
Each replicated volume requires primary group space, called local replication reserve. See Figure 19. Local Replication Reserve.
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About Backing Up and Protecting Your Data