Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

DEV007 019C RW 0 0 RW 0018 WD 0 0 A..X Consistent
DEV007 019D RW 0 0 RW 0019 WD 0 0 A..X Consistent
Package Configuration using SRDF/Synchronous or SRDF/Asynchronous
The following describes configuring a package using SRDF/Synchronous or SRDF/Asynchronous
MSC for first-time installation or pre-existing installations.
First-time installation of Metrocluster with EMC SRDF using SRDF/Synchronous
If this is a first-time installation of Metrocluster with EMC SRDF do the following steps:
1. Copy the template file that is shipped with the Metrocluster with EMC SRDF product from
/opt/cmcluster/toolkit/SGSRDF/srdf.env to the package directory.
2. Customize the template file based on the requirements in your environment.
Pre-existing Installations of Metrocluster SRDF using SRDF/Synchronous
If there is a pre-existing installation of Metrocluster with EMC SRDF and the Serviceguard applications
using SRDF/Synchronous data replication, make the following changes:
• Set new variable RDF_MODE to sync
RDF_MODE=sync
If RDF_MODE is not present, the synchronous mode is assumed.
• Unset the SYMCLI_MODE environment variable if it has been set previously.
Migration of Existing Applications from SRDF/Synchronous to SRDF/Asynchronous
EMC does not support migration on the existing applications from SRDF/Synchronous to
SRDF/Asynchronous data replication. Applications that need to use SRDF/Asynchronous mode
for data replication should configure a new device group in SRDF/Asynchronous mode. The need
to alter the data replication mode between synchronous and asynchronous for an application is
not expected in a typical Disaster Tolerant environment. Contact EMC and HP for specific
requirement to your environment.
Package Failover using SRDF/Asynchronous
The EMC Solutions Enabler provides a control operation checkpoint to confirm that the data written
in the current SRDF/Asynchronous cycle has been successfully committed to the R2 side. When a
package fails over to secondary site, Metrocluster with EMC SRDF ensures the most current data
when the SRDF link is still up. Metrocluster with EMC SRDF will invoke the action checkpoint prior
to fail over to the storage. Since the checkpoint operation will prolong the failover time for a
package to start, the duration for a package to start on R2 side will be longer. The time taken to
complete the checkpoint operation depends on the cycle time configured which determines the
amount of data outstanding on the R1 site.
Protecting against a Rolling Disaster
It is recommended to use the procedure described in the previous section for protecting against
rolling disaster situation.
Limitations and Restrictions
• Consistency Group with SRDF/Asynchronous mode is not supported.
• Domino mode is not supported in SRDF/Asynchronous mode.
• Metrocluster with ECM SRDF does not support cascading configuration using
SRDF/Asynchronous.
294 Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF