HP 418800-B21 HP StorageWorks Replication Solutions Manager 4.0.1 user guide ( - Page 107

Log disk and states The DR group log is a designated virtual disk that stores a source DR group's host writes while remote replication to the destination DR group is stopped. When replication is re-established, the contents of the log are written to the destination virtual disks within the destination DR group to synchronize the destinations with their sources. This process of writing the log disk contents to the destination in the order that the writes occurred is called merging. Log states A 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 threshold Storage 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 size When a DR group is created, the log disk is initially sized as 136 MB (Vraid1). Whenever logging occurs, the size is increased in proportion to the amount of writes. The size can increase only up to a user specified 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 of the total capacity of the virtual disks in the DR group. For example, if the DR group contains virtual disks with 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 log disks in the online disk groups with the most free space. Low-level refresh Update replication manager database entries by manually performing a discovery and refresh of individual DR groups. To update the DR group pair, apply a low-level refresh to the source and destination DR groups. The action does the following: • Performs a discovery refresh at the storage system level to gather the properties of the specified DR groups, including the log disks. • Updates the replication manager database with the new properties. Managed sets of DR groups Managed 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 permitted only on destination DR groups. See using DR group actions. HP StorageWorks Replication Solutions Manager 4.0.1 107