Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access for P9000 and XP A.11.00

Figure 27 Bi-Link Configuration with the replication link between Site2 and Site3
Continentalclusters
Primary Cluster
(Metrocluster)
Recovery Cluster
(Serviceguard cluster)
Site 1
Node Node Node Node Node Node
Site 2 Site 3
Quorum server
for recovery cluster
In Bi-Link configuration:
• Continuous Access Synchronous data replication is established to replicate data between the
arrays at Site1 and Site2 when using 3DC Sync/CAJ replication. Continuous Access Journal
data replication is established to replicate data between the arrays at Site1 and Site2 when
using 3DC CAJ/CAJ replication.
• Continuous Access Journal data replication must be established between one of the arrays
located in the Metrocluster - Site1 or Site2 - and the array located at Site3 depending on
where the Continuous Access link is configured. This replication pair is used to replicate data
to Site3 actively and will be referred as Active-CAJ pair.
Pros and Cons of Using Bi-Link and Tri-Link Configuration
In a Bi-Link configuration, the disaster tolerance to the application is lost for certain failures. For
example, in Bi-Link configuration, if the replication link exists between Site1 and Stite3 as shown
in “Bi-Link Configuration with the replication link between Site1 and Site3” (page 92), upon the
failure of Site1, the data cannot be protected at DC3. Similarly, if the replication link exists between
Site2 and Site3 as shown in “Bi-Link Configuration with the replication link between Site2 and
Site3 ” (page 93), upon the failure of Site2, the data cannot be protected at DC3. This creates a
single point of failure for data replication following a site outage.
In Tri-Link configuration, the third link ensures that replication is restored to at least one other site
for any kind of site wide outages. The Delta Resync functionality allows quick restoration of the
Overview of Continuous Access 3DC Replication Technology 93