General Metro-DR prerequisites

Prerequisites for Metro-DR between two OpenShift® Container Platform clusters.

Ensure that the following requirements are met:
Setting up the tiebreaker
  • IBM Storage Fusion HCI System must be installed in two separate data centers within a metropolitan distance from each other. A third site should be identified to host the tiebreaker, and a VM is needed to host the tie breaker. Set up the tiebreaker. For the actual procedure to setup, see Setting up the tiebreaker.
Setting up network
  • Network connectivity must be available between all three sites for both the Red Hat® OpenShift network and the IBM Storage Fusion HCI System storage network. The IBM Storage Fusion HCI System storage network is responsible for the synchronous data replication between both sites, and a high bandwidth L3 connection must be used that has less than 40 milliseconds of latency and within 150 km. It is recommended that all switches used to connect the two clusters support jumbo frames as it improves performance.
  • The IBM Spectrum Scale core pod running on every IBM Storage Fusion HCI System node at both sites is assigned an IP address on the storage network. Because the number of nodes in the cluster can grow over time, a default IP address range is automatically generated for each cluster. This default IP address range is displayed during the install GUI for each cluster. If needed, you can provide a different range of IP addresses for storage network. The IP address range must be different for each site and they should be reachable across sites.
  • By default, IBM Storage Fusion HCI System reserves the 3201 VLAN ID for the storage network. If you need to customize the VLAN ID, record the customization in the planning worksheet. IBM SSR needs the completed work sheet to do the initial configuration of the appliance.
  • For guidance on connecting both sites, see Metro-DR (Disaster Recovery).
Setting up communication between the clusters
The Metro-DR solution involves network traffic between two IBM Storage Fusion HCI System clusters and the tie breaker, firewalls for the three sites must be updated to allow traffic between each of the three endpoints in the solution.
  • Site one and site two need to allow communication between the IP addresses of the two IBM Storage Fusion HCI System clusters both on the Red Hat OpenShift network and the IBM Storage Fusion HCI System storage network. On the Red Hat OpenShift network communication across sites takes place over UDP port 4500. On the storage network communication across sites takes place over TCP ports 1191 and 12345.
  • Site one and the tie breaker site need to allow communication between the IP address on the storage network of site one cluster and the IP address of the tie breaker virtual machine. This communication takes place over 1191 and 12345.
  • Site two and the tie breaker site need to allow communication between the IP address on the storage network of the site two cluster and the IP address of the tie breaker virtual machine. This communication takes place over 1191 and 12345.
  • For Metro-DR allowed ports, see Firewall requirements for IBM Storage Fusion HCI System.
Storage network
  • A default IP range must be available out of the box for storage network.
  • If needed, you can provide a different range of IP addresses for storage network, however, note that it must be different across sites.
Admin network
Each cluster has a pod network that needs to communicate with each other in a Metro-DR setup. To achieve this communication, ensure that the pod network is different across the sites. By default, different values are available for site 1 and site 2 during installation, however, you can override them.