Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF

• To minimize contention, each device group used in the package must 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 2880 KB logical device on the Symmetrix.
For example, if a package is configured to failover across four nodes in the cluster, there must
be eight gatekeeper devices (two for each node) that are assigned to the Symmetrix device
group belonging to this package.
There must be a pool of four additional gatekeeper devices that are NOT associated with any
device group. These gatekeepers would be available for other, non-cluster uses, for example,
the Symmetrix Manager GUI and other EMC Solutions Enabler or SymAPI requests.
• This product does not support the HP OmniBack Integration with Symmetrix. The OmniBack
Integration with Symmetrix might create certain states that will cause this package to halt if a
failover occurs while the backup is in progress.
• The status of the SA/FA ports must not be checked. It is assumed that at least one PVLink is
functional. Otherwise, the VG activation will fail.
• This product might increase package startup time by 5 minutes or more. Packages with many
disk devices will take longer to start up than those with fewer devices due to the time needed
to get device status from the Symmetrix. When more than one package is starting at the same
time, the package startup time increases because of the clusters with multiple packages that
use devices on the Symmetrix.
• The value of RUN_SCRIPT_TIMEOUT in the package configuration file must be set to
NO_TIMEOUT or to a large enough value to account for the extra startup time because of the
time taken for getting status from the Symmetrix.
Data replication can utilize any extended SAN devices that support SRDF Links, for example
DWDM, Fiber Channel over Internet Protocol, and so on. However, since the network for a
Serviceguard cluster heartbeat requires a “Dark Fiber” link, it is best to utilize the DWDM
links for SRDF/asynchronous data replication. This will increase data replication bandwidth
and reliability in the Metrocluster environment.
• Consistency Group with SRDF/Asynchronous mode is not supported.
• Domino mode is not supported in SRDF/Asynchronous mode.
• Metrocluster with EMC SRDF does not support cascading configuration using
SRDF/Asynchronous.
• SRDF/Asynchronous supports all SRDF topologies including ESCON, point-to-point and switched
fabrics. For details, and to plan the connectivity based on your distance requirements, see the
EMC Network Storage Topology Guide.
Some further points 37