HP XP Continuous Access Software - Manual (Page 10)

2 Overview of XP Continuous Access Journal
XP Continuous Access Journal provides a RAID storage-based hardware solution for disaster
recovery that enables fast and accurate system recovery. After establishing XP Continuous Access
Journal operations, duplicate copies of data are automatically maintained for backup and disaster
recovery purposes. During normal XP Continuous Access 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 XP Continuous Access Journal for data
duplication and migration tasks.
XP Continuous Access Journal represents a unique and outstanding disaster recovery solution for
large amounts of data spanning multiple volumes. XP Continuous Access Journal's group-based,
update sequence consistency solution enables fast and accurate database recovery, even after a
“rolling” metropolitan area disaster, without requiring time-consuming data recovery procedures.
You can recover XP Continuous Access Journal's journal groups (volume groups) at the out of region
site with full update sequence consistency, but updates may be chronologically behind the primary
site due to the nature of asynchronous remote copy operations.
XP Continuous Access 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 XP Continuous Access Journal, data being copied is temporarily stored in journal
volumes, which are a type of logical volume. You can use XP Continuous Access 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 XP Continuous Access 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 is maintained at the remote secondary site by way of a write sequence
number assigned to the journal data. XP Continuous Access Journal reduces occurrences of pair
suspended status as a result of the superior link outage tolerance provided by disk based journal
volumes for “yet to be sent” data.
Figure 1 (page 11) provides an overview of XP Continuous Access Journal operations.
10 Overview of XP Continuous Access Journal