Planning replication for disaster recovery

Before implementing replication for disaster recovery, you must determine your recovery point objectives, application requirements, and consider the connectivity available between locations.

To implement replication for disaster recovery, consider the following:
  • Policy-based replication for disaster recovery supports only non-zero RPO and RTO. For zero RPO and RTO requirements, consider using policy-based high availability.
  • Determine the round-trip time (RTT) between the systems. As the RTT increases, the maximum throughput decreases.
  • Determine the change rate of data for applications storing data on the system. Environments with high change rates and low bandwidth may be unable to achieve low RPOs.
  • The use of replication protects data from a large-scale disaster on the site or storage systems. Consider using safeguarded snapshots in addition to replication to also provide protection against data corruption and cyber attacks.

Replication for disaster recovery requires a partnership to be configured between the systems. Partnerships for asynchronous replication can use any of the supported connectivity types. Partnerships can be configured with up to 3 other systems for disaster recovery.

IP connectivity is required between systems for management. The following TCP ports are required to be accessible on the system management IP address:
  • Port 7443 for REST API access between systems.
  • Replication setup using the management GUI requires access to both systems from the host where the web browser is running. Ensure that any firewalls between the web browser and storage systems allow inbound traffic to port 7443 and 443 on the system management IP address.
  • Additionally, IP replication requires inbound and outbound access using port 3260 on the system management IP and port 3265 on the IP addresses for the data path connections.

Policy-based replication for disaster recovery can be used with all host operating systems that are supported by IBM Storage Virtualize systems. The list of supported operating systems is on IBM System Storage Interoperation Center (SSIC).

For the best performance, configure the host multipath drivers to use SCSI ALUA or NVMe ANA.

With policy-based replication, you can replicate thin-clones and FlashCopy target volumes to the recovery system. You cannot replicate Safeguarded snapshots.

The following configuration limits and restrictions apply to policy-based replication for disaster recovery:
  • The name of a volume group cannot be changed while a replication policy is assigned.
  • Policy-based replication cannot be used with volumes that are:
    • Image mode
    • Cache disabled
    • Configured to use Transparent Cloud Tiering (TCT)
  • A volume in a volume group with a replication policy assigned cannot be:
    • Renamed
    • Resized (expanded or shrunk)
    • Migrated to image mode, or have an image mode copy added
    • Moved to a different I/O group
  • All volumes in a volume group must be in the same I/O group.