Continuous Access Journal Overview; Continuous Access Journal Software; How Continuous Access Journal Works - HP StorageWorks P9000 User Manual

1 Continuous Access Journal overview

Unless otherwise specified, the term P9000 in this guide refers to the following disk array:
P9500 Disk Array
The GUI illustrations in this guide were created using a Windows computer with the Internet Explorer
browser. Actual windows may differ depending on the operating system and browser used. GUI
contents also vary with licensed program products, storage system models, and firmware versions.
With Continuous Access Journal (Cnt Ac-J), you create and maintain a remote copy of a data
volume on a P9500 system. The remote copy is a block-for-block copy of the local storage volume.
Remote data is consistent with local data and therefore available for recovery of the local volume
should the need arise.
This guide provides instructions for planning, implementing, operating, maintaining, and
troubleshooting a Continuous Access Journal system.
The following configurations described in this document are unsupported in version 70-01-2x:
Three data center (3DC) multitarget configuration
Three data center (3DC) cascade configuration
Three data center (3DC) configuration using the delta resync function
Configuration using multiple primary and secondary storage systems

Continuous Access Journal software

With Continuous Access Journal, application data is copied to a secondary P9500 system at a
remote location. 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.
This guide provides scenarios and procedures for disaster recovery from multiple sites.
When a pair is created, the remote system will contain an asynchronous, block-for-block copy of
the local storage volume. Impact on host I/O and the primary storage system is limited, since
updates sent to the primary volume are also copied to a local journal volume. The remote system
"pulls" data from the journal volume across the communication link to the backup-volume. The
primary system is free to perform its role as a transaction processing resource rather than as
replication engine.

How Continuous Access Journal works

With Continuous Access Journal, you enable a data back up from a primary volume (P-VOL) on
the local system to a secondary volume (S-VOL) on a remote system. Continuous Access Journal
operations are performed sequentially as shown below.
Figure 1 Basic sequence in Continuous Access Journal operations
8 Continuous Access Journal overview