HP StorageWorks Continuous Access XP Journal user guide (December 2005)

64 Continuous Access XP Journal
• Primary site for Continuous Access XP Synchronous and Continuous Access XP Journal
• Secondary site for Continuous Access XP Synchronous
• Secondary site for Continuous Access XP Journal
Figure 29 3DC multi-target configuration (combining Continuous Access XP Journal with Continuous
Access XP Synchronous)
In this configuration, the primary volume at the primary site is paired with the secondary volume for
Continuous Access XP Synchronous. This primary volume is also paired with the secondary volume for
Continuous Access XP Journal. If a host at the primary site writes data to the primary volume, the data is
written to the Continuous Access XP Synchronous secondary volume in real time, synchronously with
writing from the host. The data is also written to the Continuous Access XP Journal secondary data volume,
asynchronously with writing from the host. Update sequence consistency is maintained with the Continuous
Access XP Journal secondary data volume.
Because writing from the Continuous Access XP Journal primary volume to the Continuous Access XP
Journal secondary volume is performed asynchronously with writing from the host to the primary volume,
this configuration prevents delays in the response to the host even if the Continuous Access XP Journal
primary and secondary sites are far from each other.
For more information about the hardware configuration required for 3DC multi-target configuration, see
”Hardware configurations” on page 65,
If a failure occurs in a Continuous Access XP Synchronous primary volume, which is also used as a
Continuous Access XP Journal primary data volume, you can resume business tasks using the Continuous
Access XP Synchronous secondary volume. After resuming the business tasks, remove the failure from the
primary volume and transfer the business tasks back to the primary site. For more information, see the
following:
• ”Recovering from primary site failures” on page 66
• ”Changing to 3DC multi-target configurations after recovering from primary site failures” on page 67
• ”Transferring business tasks from Continuous Access XP secondary sites to primary sites (in 3DC
cascading configurations)” on page 68
• ”Transferring business tasks from Continuous Access XP secondary sites to primary sites (in 3DC
multi-target configurations)” on page 69
If a failure occurs in the primary volume and Continuous Access XP Synchronous secondary volume, you
can resume business tasks using the Continuous Access XP Journal secondary data volume. After resuming
the business tasks, remove the failure from the primary volume and Continuous Access XP secondary
volume, and transfer the business tasks back to the primary site. For more information, see ”Recovering
from primary site and Continuous Access XP Synchronous secondary site failures” on page 70 and
”Transferring business tasks from Continuous Access XP Journal secondary sites to primary sites” on
page 71.