HP StorageWorks XP Remote Web Console Software - Manual (Page 17)

Continuous Access XP Journal user guide 17
2 Overview of Continuous Access XP Journal
Continuous Access XP Journal provides a RAID storage-based hardware solution for disaster recovery that
enables fast and accurate system recovery. After establishing Continuous Access XP Journal operations,
duplicate copies of data are automatically maintained for backup and disaster recovery purposes. During
normal Continuous Access XP Journal operations, primary data volumes remain online to all hosts and
continue processing read and write I/O operations. If a disaster or system failure occurs, you can rapidly
invoke the secondary copy of the data to allow recovery with a very high level of data integrity. You can
also use Continuous Access XP Journal for data duplication and migration tasks.
Continuous Access XP Journal represents a unique and outstanding disaster recovery solution for large
amounts of data spanning multiple volumes. Continuous Access XP Journal’s group-based, update
sequence consistency solution enables fast and accurate database recovery, even after a “rolling”
disaster, without requiring time-consuming data recovery procedures. You can recover Continuous Access
XP Journal’s journal groups (volume groups) at the secondary site with full update sequence consistency,
but updates are chronologically behind the primary site due to the nature of asynchronous remote copy
operations.
Continuous Access XP Journal provides update sequence consistency for user-defined journal groups (for
example, large databases) and protection for write-dependent applications if a disaster occurs.
When using Continuous Access XP Journal, data being copied is temporarily stored in journal volumes,
which are a type of logical volume. You can use Continuous Access XP to configure and manage highly
reliable data replication systems using journal volumes to reduce the chances of copy operation
suspensions. Copy operations can be suspended due to restrictions on data transfers from the primary site
to the secondary site.
Overview of functionality
You can use Continuous Access XP Journal to create duplicate volumes by copying data from primary
data volumes in the primary array to secondary data volumes in the secondary array at a remote
location. To duplicate volumes, perform the following steps sequentially with the primary and secondary
data volumes and journal volumes:
• Journal obtain function at the primary site
• Journal copy function between the primary and secondary sites
• Journal restore function at the secondary site
Write sequence consistency for the primary data volume at the primary site is also maintained for the
secondary data volume at the secondary site by way of a write sequence number assigned to the journal
data. Continuous Access XP Journal reduces occurrences of pair suspended status as a result of
restrictions on data transfers from the primary site to the secondary site by storing write data from the host
in the master and restore journal volumes, and provides a highly reliable duplication system.