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The cornerstone of SRM is the ability to fail over a virtual infrastructure from one datacenter to another. Understanding how this process works with the VMAX/PowerMax storage array and Symmetrix Remote Data Facility (SRDF) is an extremely important part of datacenter migration or disaster recovery.
The SRDF SRA supports two modes of SRDF replication: 2-site and 3-site (Star and Non-Star) replication. While Chapter 6 addressed 2-site replication, this chapter will deal with recovery using 3-site Star and Non-Star SRDF replication.
This chapter will discuss the following topics as they pertain to Concurrent and Cascaded SRDF/Star and SRDF/Non-Star configurations:
Failure of the compute environment
Complete failure of protected site
Failure of the compute environment
Complete failure of protected site
All SRM recovery plans, whether they are for migration or recovery, run as part of a planned workflow that ensures that systems are properly shut down and that data is synchronized with the recovery site prior to migration of the Workloads. This ensures that systems are properly quiesced and that all data changes have been completely replicated prior to starting the virtual machines at the recovery site. If, however, an error is encountered during the recovery plan execution, planned migration will stop the workflow, providing an opportunity to fix the problem that caused the error before attempting to continue.
All recovery plans in SRM include an initial attempt to synchronize data between the protection and recovery sites, even during a disaster recovery scenario. During a disaster recovery event, an initial attempt will be made to shut down the protection group’s virtual machines and establish a final synchronization between sites. This is designed to ensure that virtual machines are static and quiescent before running the recovery plan, to minimize data loss where possible during a disaster. If the protected site is no longer available, the recovery plan will continue to execute and will run to completion even if errors are encountered. This minimizes the possibility of data loss while still enabling disaster recovery to continue, balancing the requirement for virtual machine consistency with the ability to achieve aggressive recovery point/time objectives.
Figure 131 shows the recovery plan execution wizard.
Note: If the advanced option, ReverseReplicationDuringRecovery is enabled the recovery site SRA will perform all reprotect operations relating to SRDF reconfiguration during the recovery process and reprotect will therefore only perform recovery plan/protection group swaps. Refer to the sections on reprotection in this chapter for information on what operations are executed during recovery when this option is enabled.