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IBM XIV Storage System Copy Services and Migration

IBM XIV Storage System: Copy Services and Migration - Common ...

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6.5.2 Mirroring ongoing operationFollowing the completion of the initialization phase, the master examines the synchronizationstatus at scheduled intervals <strong>and</strong> determines the scope of the synchronization. The followingprocess occurs whenever a synchronization is started:1. A snapshot of the master is created.2. The master calculates the differences between the master snapshot <strong>and</strong> the most recentmaster snapshot that is synchronized with the slave.3. The master establishes a synchronization process called a sync job that replicates thedifferences from the master to the slave. Only data differences are replicated.Details of this process can be found in 6.6, “Detailed asynchronous mirroring process” onpage 173.6.5.3 Mirroring consistency groupsThe synchronization status of the consistency group is determined by the status of allvolumes pertaining to this consistency group.► The activation <strong>and</strong> deactivation of a consistency group affects all of its volumes.► Role updates concerning a consistency group affect all of its volumes.►►It is impossible to directly activate, deactivate, or update the role of a given volume within aconsistency group.It is not possible to directly change the schedule of an individual volume within aconsistency group.6.5.4 Mirroring special snapshotsThe status of the synchronization process <strong>and</strong> the scope of the sync job are determinedthrough the use of the following two special snapshots:► Most_recent snapshotThis snapshot is the most recent taken of the master system, either a volume orconsistency group. This snapshot is taken prior to the creation of a new sync job. Thisentity is maintained on the master system only.► Last_replicated snapshotThis is the most recent snapshot that has been fully synchronized with the slave system.This snapshot is duplicated from the most_recent snapshot after the sync job is complete.This entity is maintained on both the master <strong>and</strong> the slave systems.Snapshot life-cycleThroughout the sync job life cycle, the most_recent <strong>and</strong> last_replicated snapshots are created<strong>and</strong> deleted to denote the completion of significant mirroring stages.172 <strong>IBM</strong> <strong>XIV</strong> <strong>Storage</strong> <strong>System</strong>: <strong>Copy</strong> <strong>Services</strong> <strong>and</strong> <strong>Migration</strong>

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