3dc cascade configuration – HP XP7 Storage User Manual
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B Configurations with Continuous Access Synchronous Z
Continuous Access Journal Z and Continuous Access Synchronous Z can share the same data
volumes. Using Continuous Access Journal Z and Continuous Access Synchronous Z can extend
disaster recovery options to a third data center.
This appendix provides planning and setup information for sharing Continuous Access Journal Z
volumes with Continuous Access Synchronous Z. It describes four Continuous Access Journal
Z/Continuous Access Synchronous Z configurations.
Note that the term “P-VOL” indicates the primary volume, and “S-VOL” indicates the secondary
volume. These terms are used for both Continuous Access Journal Z (Cnt Ac-J Z) and Continuous
Access Synchronous Z (Cnt Ac-S Z).
Sharing volumes with Continuous Access Synchronous Z
Like Cnt Ac-J Z, a Cnt Ac-S Z pair maintains a copy of the production volume in a second location.
However, unlike Cnt Ac-J Z, Cnt Ac-S Z’s secondary volume (S-VOL) is synchronous, and the
secondary system is located within the same general region as the local site.
Creating a Cnt Ac-J Z backup and a Cnt Ac-S Z backup ensures that a copy in a third location is
available in the event that the local site, and possibly one of the remote sites, fail.
Cnt Ac-J Z and Cnt Ac-S Z can be used and configured in a variety of ways. The following describes
four principle configurations. These are covered in detail in this appendix.
•
In a 3-data-center cascade configuration (3DC cascade), three data centers are used — the
Cnt Ac-S Z production site, the Continuous Access Synchronous Z/Continuous Access Journal
Z intermediate site, and the distant Cnt Ac-J Z remote site. The figure in the
provides an illustration. With this configuration, you can locate the
Cnt Ac-S Z synchronous site near the local site to lower I/O response time, while the Cnt Ac-J
Z backup provides a disaster recovery solution at a remote site.
•
In a 3-data-center multi-target configuration (3DC multi-target), the production volume is shared
by the Cnt Ac-S Z and Cnt Ac-J Z. This volume is the primary volume (P-VOL) for both at the
local site. The targets of each system are located at different remote sites. They provide the
Cnt Ac-S Z solution and the Cnt Ac-J Z asynchronous disaster recovery solution. The Cnt Ac-S
Z remote site is at an intermediate location, the Cnt Ac-J Z remote site is at a distant location.
This is illustrated in
“3DC multi-target configuration ” (page 143)
•
Another use of the 3DC multi-target is the Cnt Ac-J Z Delta Resync pair, which provides a quick
way to regain a long distance copy after disaster in the event that the Continuous Access
Synchronous Z/Continuous Access Journal Z P-VOL becomes unusable. In this case, the host
continues I/O operations at the intermediate Cnt Ac-S Z S-VOL site. With a second Cnt Ac-J
Z pair previously set up between the Cnt Ac-S Z S-VOL and the Cnt Ac-J Z S-VOL, only
differential data needs to be copied to the Cnt Ac-J Z S-VOL. Delta resync is illustrated in
“Delta resync configuration ” (page 144)
.
3DC cascade configuration
In a multi-target configuration, data is copied from the local site to two remote sites.As illustrated
below, the Cnt Ac-S Z P-VOL is the primary production volume in a 3DC cascade configuration.
The Cnt Ac-S Z S-VOL is located at an intermediate site that is near the local site.
The host issues an update to the Cnt Ac-S Z primary volume (P-VOL), which is copied synchronously
to the S-VOL. The Cnt Ac-J Z system copies the synchronous S-VOL data to the Cnt Ac-J Z remote
site.
Data in the Cnt Ac-J Z S-VOL is an asynchronous copy of the Cnt Ac-S Z P-VOL. Depending on
RPO and bandwidth, Cnt Ac-J Z S-VOL data can be very close to P-VOL data. As always with Cnt
Ac-J Z, data consistency is ensured.
Sharing volumes with Continuous Access Synchronous Z
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