HP XP7 Storage - Manual (Page 8)

1 Continuous Access Journal overview
With Continuous Access Journal (Cnt Ac-J), you create and maintain a remote copy of a data
volume on a HP XP7 Storage system.
This guide provides instructions for planning, configuring, operating, maintaining, and
troubleshooting a Continuous Access Journal system.
Important: Procedures in this manual are tailored to the Remote Web Console (RWC) GUI. When
using this GUI, “Local Storage System” displays for the system you have accessed on the RWC
server.
As a result, if you access the remote site’s RWC server, the GUI displays information for the pair’s
remote (secondary) system under “Local Storage System”. Likewise, the GUI in this case identifies
the storage system connecting to the accessed system as the “Remote Storage System”.
However, this manual uses the terms ”primary storage system” or “primary system” for the storage
system in which the primary volume (P-VOL) is located in the local site, and “secondary storage
system” or “secondary system” for the storage system in which the secondary volume (S-VOL) is
located in the remote site, unless otherwise noted.
Continuous Access Journal software
With Continuous Access Journal, you copy application data from its primary storage volume in
the primary XP7 storage system to a secondary system at a remote location. The volume in the
secondary system is the secondary volume and is an asynchronous block-for-block copy of the
primary storage volume. The copied data is consistent with primary volume data and therefore
available for recovering the primary volume if the need arises.
Continuous Access Journal is designed to support a remote site hundreds and even thousands of
miles from the local site, making recovery from region-wide disasters possible.
Continuous Access Journal is also designed to limit impact on the primary system. Updates sent
from a host to the primary production volume on the primary system are copied to a master journal
volume. The secondary system “pulls” data from the journal volume across the communication link
to the backup-volume, the secondary volume. The primary system is free to perform its role as a
transaction processing resource rather than as a replication engine.
How Continuous Access Journal works
Remote replication occurs using journal volumes on the primary and secondary systems.
Figure 1 Basic sequence in Continuous Access Journal operations
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The journal volume on the primary system is called the “master journal volume”.
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The journal volume on the secondary system is called the “restore journal volume”.
Replication occurs in the following sequence:
8 Continuous Access Journal overview