Sharing volumes with continuous access synchronous, 3dc cascade configuration, Configurations – HP XP7 Storage User Manual
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B Configurations with Continuous Access Synchronous
Continuous Access Journal and Continuous Access Synchronous can share the same data volumes.
Using Continuous Access Journal and Continuous Access Synchronous can extend disaster recovery
options to a third data center.
This appendix provides planning and setup information for sharing Continuous Access Journal
volumes with Continuous Access Synchronous. It describes four Continuous Access
Journal/Continuous Access Synchronous 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 (Cnt Ac-J) and Continuous Access
Synchronous (Cnt Ac-S).
Sharing volumes with Continuous Access Synchronous
Like Cnt Ac-J, a Cnt Ac-S pair maintains a copy of the production volume in a second location.
However, unlike Cnt Ac-J, Cnt Ac-S’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 backup and a Cnt Ac-S 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 and Cnt Ac-S 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 production site, the Continuous Access Synchronous/Continuous Access Journal
intermediate site, and the distant Cnt Ac-J remote site. The figure in the
provides an illustration. With this configuration, you can locate the
Cnt Ac-S synchronous site near the local site to lower I/O response time, while the Cnt Ac-J
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 and Cnt Ac-J. 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
solution and the Cnt Ac-J asynchronous disaster recovery solution. The Cnt Ac-S remote site
is at an intermediate location, the Cnt Ac-J remote site is at a distant location. This is illustrated
in
“3DC multi-target configuration ” (page 126)
•
Another use of the 3DC multi-target is the Cnt Ac-J Delta Resync pair, which provides a quick
way to regain a long distance copy after disaster in the event that the Continuous Access
Synchronous/Continuous Access Journal P-VOL becomes unusable. In this case, the host
continues I/O operations at the intermediate Cnt Ac-S S-VOL site. With a second Cnt Ac-J
pair previously set up between the Cnt Ac-S S-VOL and the Cnt Ac-J S-VOL, only differential
data needs to be copied to the Cnt Ac-J S-VOL. Delta resync is illustrated in
.
•
In a 2-data-center configuration (2DC), data is copied from the Cnt Ac-S P-VOL to an
intermediate site, though not to the Cnt Ac-S S-VOL. Instead, the data is copied to the Cnt Ac-J
master journal volume. This results in an asynchronous copy that side-steps the Cnt Ac-S S-VOL,
and thus enhances overall transfer speed to the Cnt Ac-J S-VOL. This is illustrated in
center configuration” (page 134)
.
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 P-VOL is the primary production volume in a 3DC cascade configuration. The
Cnt Ac-S S-VOL is located at an intermediate site that is near the local site.
The host issues an update to the Cnt Ac-S primary volume (P-VOL), which is copied synchronously
to the S-VOL. The Cnt Ac-J system copies the synchronous S-VOL data to the Cnt Ac-J remote site.
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Configurations with Continuous Access Synchronous