HP XP Continuous Access Software - Manual (Page 23)

Continuous Access XP Journal secondary data volumes). The secondary array continuously issues
read journal commands to the primary array in order to copy journals. For Command View XP,
the secondary management station should be connected to the secondary array at the secondary
site on a separate LAN. The secondary array should also be attached to a host system to:
• Report sense information if a problem with a secondary data volume or secondary array
occurs.
• Provide disaster recovery capabilities.
The local array can function simultaneously as a primary array for one or more primary data
volumes and as a secondary array for one or more secondary data volumes if the remote copy
connections and Fibre Channel interface ports are properly configured. You can use Continuous
Access XP Journal to specify the secondary array from the connected primary array. You can
perform Continuous Access XP Journal operations on all internal LDEVs except Command View XP
or XP Remote Web Console command devices. For more information about local array command
devices, see the HP StorageWorks LUN Configuration and Security Manager XP user guide for the
XP12000/XP10000/SVS200.
NOTE:
When configuring a journal group pair, you must specify the serial numbers of the primary and
secondary arrays. You must specify different serial numbers for the primary array and secondary
array for a journal group pair. If you must specify the same serial number, contact your HP account
support representative.
Journal groups
A journal group consists of two or more data volumes and journal volumes. You can use a journal group
to tailor Continuous Access XP Journal for your unique business content. A journal volume in the primary
array is referred to as a master journal volume. A journal volume in the secondary array is referred to as
a restore journal volume. The data volume in the master journal group is called the primary data volume.
The data volume in the restore journal group is similarly called the secondary data volume.
The data update sequence from the host is managed and ensured at the level of a matched set of a
master and restore journal group. The journal numbers of paired master and restore journal groups can
be different. A particular data volume or journal volume can belong to only one journal group.
Data volume pairs
Continuous Access XP Journal performs remote copy operations for data volume pairs that you have
created. Each Continuous Access XP Journal pair consists of one primary data volume and one
secondary data volume, which are typically located in different arrays. Continuous Access XP Journal
primary data volumes are the primary volumes (LUs) containing the original data. Continuous Access XP
Journal secondary volumes are the secondary volumes (LUs) containing the remotely duplicated data.
During normal Continuous Access XP Journal operations, the primary data volume remains available
to hosts at all times for read and write I/O operations. During normal Continuous Access XP Journal
operations, the secondary array rejects all host-requested write I/Os directed to the secondary data
volume. The secondary data volume write enable option allows write access to a secondary data volume
while the pair is split and can use secondary and primary data volume track maps to later resynchronize
the pair (see Secondary data volume write option ).
Continuous Access XP Journal data volume pairs also supports LUN Expansion (LUSE), Volume Manager
and Cache LUN XP, which allows Continuous Access XP Journal to meet a variety of user needs by way of
data copying and data migration. This ensures that all user data can be backed up or duplicated. See
Logical unit (LU) types for more information about LU requirements and support.
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