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

Physical Data Replication for ContinentalClusters Using Continuous Access XP
Failback Scenarios
Chapter 6 315
Failback Scenarios
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 HP StorageWorks E XP
series disk arrays and Continuous Access (CA). In Chapter 5, “Building a
Continental Cluster,” there is a discussion of failback mechanisms and
methodologies in “Restoring Disaster Tolerance” on page 256.
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 XP disk array
or the operating systems of the systems at the primary site.
Scenario 2
The primary site XP disk array experienced a catastrophic hardware
failure and all data was lost on the array.
Failback in Scenarios 1 and 2
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. Each ContinentalClusters package control script will evaluate
the status of the XP paired volumes. Since neither the systems nor the
XP disk array at the primary site are accessible, the control file will
initially report the paired volumes with a local status of SVOL_PAIR or
SVOL_PSUE (in ASYNC mode) and a remote status of EX_ENORMT, PSUE or
PSUS, indicating that there is an error accessing the primary site. The
control file script is programmed to handle this condition and will enable
the volume groups, mount the logical volumes, assign floating IP
addresses and start any processes as coded into the script.