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9 Using Dell PS Series Asynchronous Replication | TR1052
Because replicas and failback snapshots are a representation of the volume data at a precise point in time,
the group must maintain that state until the replication completes. To allow the volume to remain online
and in use during this time, the group uses the local replication reserve to temporarily track changes to the
volume while the operation is underway. When the replication is complete, the local replication reserve
space is freed, unless the volume was configured to keep a failback snapshot (see section 2.7).
Current replica volume reserve (in MB/GB/TB) on the secondary group, is the reserved space for
replication on the volume.
Total replica reserve is the amount of space reserved for the replica set within the configured delegated
space on the secondary group. Total replica reserve is a percentage of the current replica volume reserve
that provides additional space for replicas. If the current replica reserve is 1 GB, and you specify 200% for
total replica reserve, the total replica reserve size is 2 GB. If the current replica volume reserve increases to
4 GB, then the total replica reserve size also increases to 8 GB. The total replica reserve for a volume can
potentially limit the number of replicas that are kept. To prevent older replicas from being deleted, space
can automatically be borrowed (section 5.1.3.1) from other sources when the total replica reserve is
consumed.
Figure 2 Examples of group space usage (1)
Figure 3 Examples of group space usage (2)