IBM XIV Storage System Copy Services and Migration

1.4 Snapshot with Remote MirrorXIV has a special snapshot (shown in Figure 1-47) that is automatically created by thesystem. During the recovery phase of a Remote Mirror, the system creates a snapshot on thetarget to ensure a consistent copy.Important: This snapshot has a special deletion priority and is not deleted automatically ifthe snapshot space becomes fully utilized.When the synchronization is complete, the snapshot is removed by the system because it isno longer needed. The following list describes the sequence of events to trigger the creationof the special snapshot. Note that if a write does not occur while the links are broken, thesystem does not create the special snapshot. The events are:1. Remote Mirror is synchronized.2. Loss of connectivity to remote system occurs.3. Writes continue to the primary XIV Storage System.4. Mirror paths are reestablished (here the snapshot is created) and synchronization starts.Figure 1-47 Special snapshot during Remote Mirror synchronization operationFor more details about Remote Mirror refer to Chapter 5, “Synchronous Remote Mirroring” onpage 125.Important: The special snapshot is created regardless of the amount of pool space on thetarget pool. If the snapshot causes the pool to be overutilized, the mirror remains inactive.The pool must be expanded to accommodate the snapshot, then the mirror can bereestablished.Chapter 1. Snapshots 33