Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building a Metropolitan Cluster Using MetroCluster/SRDF
R1/R2 Swapping
Chapter 4 175
R1/R2 Swapping
This section shows how the R1/R2 swapping can be done via
MetroCluster/SRDF package and manual procedures. Each of these
allow you to swap the SRDF personality for each device designations of a
specified devicegroup, where each source R1 device(s) becomes a target
R2 device(s) and a target R1 device(s) becomes a source R1 device(s).
R1/R2 Swapping Using MC/SRDF Packages
The MetroCluster/SRDF package can be configured to automatically do
R1/R2 swapping upon package failover. To enable R1/R2 swapping in
the package, set the environment variable AUTOSWAPR2 in the
<package_name>_srdf.env file to 1. Since the swap is done
automatically upon package start up, the MetroCluster/SRDF software
will only do the swap if the Symmetrix frames and the SRDF links
between them are working properly, that is, the SRDF state of the device
group is in Synchronized state. If the failover and swap operations are
successful, the devices will have their personalities switched, and the
data replication will continue from the new R1 devices to the new R2
devices.
Note that when failing over a package with R1/R2 swapping, the package
startup time will be longer than without swapping.
R1/R2 Swapping Using Manual Procedures
You can also do R1/R2 swapping manually. There are two scenarios
where manual swapping is supported by MetroCluster/SRDF.
Scenario 1: In this scenario, the package failover is due to host failure or
due to planned downtime maintenance. The SRDF links and the
Symmetrix frames are still up and running. Because the package startup
time will be longer if the swapping is done automatically, the user can
choose not to have the swapping done by the package and then manually
execute the swapping after the package is up and running on the R2 side.
Following is the manual procedure to swap the devices personalities and
change the direction of the data replication.
On the host that connects to the R2 side use the following steps: