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

Physical Data Replication for ContinentalClusters Using EMC SRDF
Maintaining the EMC SRDF Data Replication Environment
Chapter 7358
devices) until the SRDF link is restored, or manual intervention is
undertaken to disable Domino Mode. Applications may fail or may
continuously retry the I/Os (depending on the application) if Domino
Mode is enabled and the SRDF link fails.
• SRDF firmware has been configured and hardware has been
installed on both Symmetrix units
• R1 and R2 devices must be correctly defined and assigned to the
appropriate host systems in the internal configuration that is
downloaded by EMC
• While the cluster is running, all Symmetrix devices that belong to
the same MC/ServiceGuard package, and defined in a single SRDF
device group must be in the same state at the same time. Manual
changes of these states can cause the package to halt due to
unexpected conditions. In general, it is recommended that no
manual change of states be performed while the package and the
cluster are running.
• A single Symmetrix device group must be defined for each package
on each host that is connected to the Symmetrix. The disk special
device file names for all Volume Groups that belong to the package
must be defined in one Symmetrix device group for both R1 side and
R2 side.
The Symmetrix device group name must be the same on each host for
both R1 side and R2 side. This group name is placed in the shell
script array variables DEVICE_GROUP.
Although the name of the device group must be the same on each
node, the special device file names specified may be different on each
node.
Symmetrix Logical Device names MUST be default names of the
form “DEVnnn” (e.g., DEV001). Do not use the option for creating
your own device names.
See the SymCLI manual, and the sample convenience scripts in the
Samples-CC directory included with this toolkit.
• To minimize contention, each device group used in the package
should be assigned two unique gatekeeper devices on the Symmetrix
for each host where the package will run. These gatekeeper devices
must be associated with the Symmetrix device groups for that
package. The gatekeeper devices are typically a 2 MB logical device
on the Symmetrix.