HP XP P9500 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 P9500 storage system.
This guide provides instructions for planning, configuring, operating, maintaining, and
troubleshooting a Continuous Access Journal system.
Continuous Access Journal software
With Continuous Access Journal, you copy application data to a secondary P9500 system at a
remote location. The remote volume is an asynchronous block-for-block copy of the local storage
volume. The copied data is consistent with local data and therefore available for recovering the
local volume if the need arises.
Continuous Access Journal is designed to support a secondary 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 local system. Updates sent from
a host to the primary production volume on the local system are copied to a local journal volume.
The remote system “pulls” data from the journal volume across the communication link to the
backup-volume, called the secondary volume. The local system is free to perform its role as a
transaction processing resource rather than as a replication engine.
NOTE: The ”local” system is also referred to as the “primary” system.
The “remote” system is also referred to as the “secondary” system.
The production volume on the primary system receives and stores the data sent from the host. This
volume is commonly referred to as the “primary volume”, or “P-VOL”.
The backup volume on the secondary system stores the data copied from the primary system, and
is commonly referred to as the “secondary volume”, or “S-VOL”.
How Continuous Access Journal works
Remote replication occurs using journal volumes on the local and remote systems.
Figure 1 Basic sequence in Continuous Access Journal operations
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The journal volume on the local system is called the “master journal volume”.
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The journal volume on the remote system is called the “restore journal volume”.
Replication occurs in the following sequence:
8 Continuous Access Journal overview