Log disk and statesThe DR group log is a designated virtual disk that stores a source DR group’s host writes while remotereplication to the destination DR group is stopped.When replication is re-established, the contents of the log are written to the destination virtual disks withinthe destination DR group to synchronize the destinations with their sources. This process of writing the logdisk contents to the destination in the order that the writes occurred is called merging.Log statesA DR group log can be in one of the following states:• Unused (Normal). No source virtual disk in the DR group is logging or merging.• Logging. At least one source virtual disk in the DR group is logging but none are merging.• Merging. At least one source virtual disk in the DR group is merging and logging.Log-full thresholdStorage system controller software considers a log disk full when any of the following occurs:• No free space remains in the disk group.• The log disk reaches 2 TB of Vraid1 (4 TB total).• The log disk reaches its maximum size.When the log disk is declared full, DR group members are marked for full copy and the log disk is deleted.Maximum log disk sizeWhen a DR group is created, the log disk is initially sized as 136 MB (Vraid1). Whenever loggingoccurs, the size is increased in proportion to the amount of writes. The size can increase only up to a userspecified maximum value or to the controller software’s default maximum value.The default maximum value depends on the controller software version and is expressed as a multiple ofthe total capacity of the virtual disks in the DR group. For example, if the DR group contains virtual diskswith a total of 10 GB and the multiple is 1x then the default maximum size for the log disk is 10 GB.For specific values, see Controller software features - remote replication.When creating disk groups, ensure there is sufficient space for log disks to expand to their maximum size.HP recommends creating DR group log disks in near-line disk groups, if available. Otherwise, create logdisks in the online disk groups with the most free space.Low-level refreshUpdate replication manager database entries by manually performing a discovery and refresh ofindividual DR groups. To update the DR group pair, apply a low-level refresh to the source anddestination DR groups.The action does the following:• Performs a discovery refresh at the storage system level to gather the properties of the specifiedDR groups, including the log disks.• Updates the replication manager database with the new properties.Managed sets of DR groupsManaged sets of DR groups require careful planning. Consider the following guidelines.• Some DR group actions are permitted only on source DR groups; other actions are only permittedonly on destination DR groups. See using DR group actions.HP StorageWorks Replication Solutions Manager 4.0.1 107
