3DC cascade configuration
As illustrated below, the Continuous Access Synchronous P-VOL is the primary production volume
in a 3DC cascade configuration. The Continuous Access Synchronous S-VOL is located at an
intermediate site that is near the primary site.
The host issues an update to the Continuous Access Synchronous primary volume (P-VOL), which
is copied synchronously to the S-VOL. The Continuous Access Journal system copies the synchronous
S-VOL data to the Continuous Access Journal remote site.
Data in the Continuous Access Journal S-VOL is an asynchronous copy of the Continuous Access
Synchronous P-VOL. Depending on RPO and bandwidth, Continuous Access Journal S-VOL data
can be very close to P-VOL data. As always with Continuous Access Journal, data consistency is
insured.
Figure 19 3DC cascade (3DC cascade)
Failure recovery occurs as follows:
If a failure occurs at the Continuous Access Synchronous P-VOL, business continues because
data in the Continuous Access Journal S-VOL is restored to the production system via the
intermediate volume, if needed. Update sequence integrity is insured.
If a failure occurs at both Continuous Access Synchronous P-VOL and S-VOL, an implemented
disaster recovery plan would redirect host activities to the Continuous Access Journal S-VOL.
See
"Recovery in a 3DC cascade configuration " (page 97)
procedures.
Prerequisite information for 3DC cascade
P9500 must be installed at the local, Continuous Access Synchronous intermediate, and
Continuous Access Journal remote sites.
RAID Manager is recommended at all sites.
Remote Web Console is required at all sites.
Host application
◦
◦
Continuous Access Synchronous
Continuous Access Synchronous primary volume (P-VOL), the primary production volume
◦
◦
Continuous Access Synchronous fence level must be Data.
The intermediate site requires the following:
◦
Continuous Access Synchronous
Continuous Access Journal
◦
◦
Continuous Access Synchronous S-VOL = Continuous Access Journal P-VOL
Continuous Access Journal master journal volume
◦
136 Continuous Access Journal configurations with Continuous Access Synchronous
for recovery information and