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

Physical Data Replication for ContinentalClusters Using EMC SRDF
Failback Scenarios
Chapter 7348
Failback Scenarios
There is no failback counterpart to the “pushbutton” failover from the
primary cluster to the recovery cluster. Failback is very dependent on
the original nature of the failover, the state of primary and secondary
Symmetrix SRDF volumes (R1 and R2) and the condition of the primary
cluster. In Chapter 5, “Building a Continental Cluster,” there is a
discussion of failback mechanisms and methodologies in the section
“Restoring Disaster Tolerance” on page 256.
The goal of HP ContinentalClusters is to maximize system and
application availability. However, even systems configured with
ContinentalClusters can experience hardware failures at the primary
site or the recovery site, as well as the hardware or networking failures
connecting the two sites. The following discussion addresses some of
those failures and suggests recovery approaches applicable to
environments using data replication provided by Symmetrix Disk Arrays
and Symmetrix Remote Data Facility SRDF.
Scenario 1
The primary site has lost power, including backup power (UPS), to both
the systems and disk arrays that make up the MC/ServiceGuard Cluster
at the primary site. There is no loss of data on either the Symmetrix or
the operating systems of the systems at the primary site.
After reception of the ContinentalClusters alerts and alarm, the
administrators at the recovery site follow the prescribed processes and
recovery procedures to start the protected applications on the recovery
cluster. The ContinentalClusters control file will evaluate the status of
the R1 primary and R2 paired group volumes.
The command symrdf list will display the paired status of the links.
Example-- Dev 001 has failed over Device Group pkgCCB_r1
Symmetrix ID: 000183500021
Local Device View
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STATUS M O D E S RDF S T A T E S
Sym RDF --------- ------------ R1 Inv R2 Inv
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