Planned Failback from the Remote DR Center to the Production Center (Cascading Network)

This section shows how to manually switch production services back from the remote DR center to the production center on a synchronous and asynchronous or asynchronous and asynchronous cascading network.

Prerequisites

eReplication in the remote DR center has been used to switch services from the production center to the remote DR center as planned.
If the network is in synchronous and asynchronous mode, synchronous remote replication has been performed between storage arrays in the production center and the same-city DR center. The production storage array is the source (primary) array of the synchronous replication. Asynchronous remote replication has been performed between the same-city and remote DR centers, and the asynchronous replication is in the Split state. The DR storage array in the same-city DR center is the source (primary) array.
If the network is in asynchronous and asynchronous mode, synchronous remote replication has been performed between storage arrays in the production center and the same-city DR center. The production storage array is the source (primary) array of the asynchronous replication. Asynchronous remote replication has been performed between the same-city and remote DR centers, and the asynchronous replication is in the Split state. The DR storage array in the same-city DR center is the source (primary) array.
In the Oracle application, the database is disabled but the cluster is enabled by default on the eReplication Agent. If you need to disable clusters, modify the configuration of disabling clusters. For details, see Changing the Configuration of Stopping the Oracle Cluster.
In a DR Star network, before performing planned migration, log in to DeviceManager and ensure that the running status of the DR Star network is Enabled.
The datastore name cannot contain Chinese characters.

Context

To perform failback in a cascading network, perform the following steps:

Synchronize production data from the remote DR center to the same-city DR center.
Restore asynchronous remote replication relationships between storage arrays from the same-city DR center to the remote DR center.
Synchronize data from the same-city DR center to the production center.
Restore synchronous or asynchronous remote replication relationships between storage arrays from the production center to the same-city DR center.
Test production services on the host in the production center.
On eReplication in the same-city DR center, restore DR configurations.

Procedure

Perform primary/secondary switchover for remote replication between the production center and the same-city DR center and that between the same-city and remote DR centers.
1. Log in to the management software of the storage array in the production center and perform primary/secondary switchover for remote replication.
  1. Log in to the management software of the storage array in the remote DR production and split the remote replication.
  2. Deselect Protection for Secondary Resource for remote replication.
  3. Perform primary/secondary switchover for remote replication between the production center and intra-city DR center.
2. Log in to the management software of the storage array in the same-city DR center and perform primary/secondary switchover for the asynchronous remote replication between storage arrays in the same-city and remote DR centers.
  Figure 1 and Figure 2 show the remote replication relationships between storage arrays in the production, same-city DR, and remote DR centers before and after the primary/secondary switchover, respectively.
  
  Figure 1 Remote replication relationships before the primary/secondary switchover on a synchronous and asynchronous network
  
  Figure 2 Remote replication relationships before the primary/secondary switchover on an asynchronous and asynchronous network
  
  Remote replication in the Split state will not synchronize data.
  
  Remote replication relationships must be set in the Split state before the primary/secondary switchover.
  
  In a remote replication relationship, the source array is the primary end and the target array is the secondary end.
  
  Figure 3 and Figure 4 show the remote replication relationships between storage arrays in the production, same-city DR, and remote DR centers before and after the primary/secondary switchover, respectively.
  - If the network is in synchronous and asynchronous mode, synchronous remote replication is performed between storage arrays in the production and same-city DR centers. The DR storage array in the same-city DR center is the source (primary) array of the replication, and the replication relationship is in the Split state. Asynchronous remote replication is performed between the same-city and remote DR centers, and the replication relationship is in the normal state. The DR storage array in the remote DR center is the source (primary) array of the replication.
  - If the network is in asynchronous and asynchronous mode, asynchronous remote replication is performed between storage arrays in the production and same-city DR centers and between those in the same-city and remote DR centers. The remote replication relationships are in the Normal state. Asynchronous remote replication is performed between the same-city and remote DR centers, and the replication relationship is in the Normal state. The DR storage array in the remote DR center is the source (primary) array of the replication.
    Figure 3 Remote replication relationships after the primary/secondary switchover on a synchronous and asynchronous network
    
    Figure 4 Remote replication relationships after the primary/secondary switchover on an asynchronous and asynchronous network
Synchronize service data from the remote disaster recovery center to the storage array in the same-city disaster recovery center.
1. Log in to a host or VM in the remote DR center and stop services.
  - If the protected objects are databases, close the application system and unmount disks.
  - If the protected objects are local file systems, stop programs and files on the DR host.
  - If the protected objects are VMware VMs, close VMs and uninstall datastores.
2. Log in to the management software of the storage array in the remote DR center and delete mapping views between LUNs and the DR host.
3. Select Enable Protection for Secondary Resource for asynchronous remote replication.
4. Synchronize data for asynchronous remote replication.
After data is synchronized, split asynchronous remote replication's between storage arrays in the remote and same-city DR centers.
1. Log in to the management software of the storage array in the remote DR center and split the asynchronous remote replication.
2. Select Disable Protection for Secondary Resource for asynchronous remote replication.
Log in to the storage array in the same-city DR center and restore the asynchronous remote replication relationship between storage arrays in the same-city and remote DR centers.
1. Log in to the storage array in the same-city disaster recovery center and perform primary/secondary switchover for the asynchronous remote replication between storage arrays in the same-city disaster recovery center and the remote disaster recovery center.
2. Select Enable Protection for Secondary Resource for asynchronous remote replication.
3. Synchronize data for asynchronous remote replication.
The asynchronous remote replication relationship between storage arrays in the same-city and remote DR centers is restored, and the storage array in the same-city DR center is the primary array of the replication.
Log in to the management software of the storage array in the same-city DR center, and synchronize data for the synchronous remote replication's between storage arrays in the same-city DR and production centers.
1. Log in to the management software of the storage array in the same-city DR center, select Enable Protection for Secondary Resource for the synchronous or asynchronous replication's between storage arrays in the same-city DR and production centers.
2. Synchronize data for synchronous or asynchronous remote replication.
Remote replication is restored between storage arrays in the remote DR, same-city DR, and production centers, and data is consistent between the three centers.
After data is synchronized, log in to the storage array of the production center and perform primary/secondary switchover between storage arrays in the production and same-city DR centers.
The storage array in the production center becomes the primary array of the replication.
- If the network is in synchronous and asynchronous mode, the primary/secondary switchover can be directly performed.
- If the network is in asynchronous and asynchronous mode, the three operations must be performed in sequence: primary/secondary switchover, Enable Protection for Secondary Resource selection, and data synchronization for asynchronous remote replication.
Remote replication is successfully restored between the three data centers in a cascading network:
- If the network is in cascading mode, asynchronous remote replication is performed between storage arrays in the production and same-city DR centers. The storage array in the production center is the primary array of the synchronous replication. Asynchronous remote replication is performed between storage arrays in the same-city and remote DR centers, and the storage array in the same-city DR center is the primary array of the replication.
- If the network is in synchronous and asynchronous mode, asynchronous remote replication is performed between storage arrays in the production and remote DR centers. The storage array in the production center is the primary array of the replication. Asynchronous remote replication is performed between storage arrays in the same-city and remote DR centers, and the storage array in the same-city DR center is the primary array of the replication.
Test production services in the production center.
1. Log in to the management software of the storage array in the production center and restore mapping views between LUNs and the production host.
2. Log in to the production host or VM, and test services.
  - If the protected objects are databases, mount disks, start application systems, and test services.
  - If the protected objects are local file systems, start programs and files on the DR host, and test services.
  - If the protected objects are VMware VMs, attach datastores, start VMs, and test services.
Restore DR configurations.
1. Log in to eReplication in the same-city DR center, refresh its managed storage arrays and hosts, delete invalid DR protected groups and recovery plans.
2. Re-create DR protected groups and recovery plans.

Result

After service failback:

Services on the production center can be accessed properly.
In a cascading network in synchronous and asynchronous network, data is synchronously replicated from the production center to the same-city DR center, and is asynchronously replicated from the same-city DR center to the remote DR center.
In an asynchronous and asynchronous cascading network, data is synchronously replicated from the production center to the same-city DR center, and is asynchronously replicated from the same-city DR center to the remote DR center.
The DR management server completes the DR in the cascading network.