Red Hat Summit第5章 Disaster recovery with stretch cluster for OpenShift Data Foundation
Red Hat OpenShift Data Foundation deployment can be stretched between two different geographical locations to provide the storage infrastructure with disaster recovery capabilities. When faced with a disaster, such as one of the two locations is partially or totally not available, OpenShift Data Foundation deployed on the OpenShift Container Platform deployment must be able to survive. This solution is available only for metropolitan spanned data centers with specific latency requirements between the servers of the infrastructure.
The stretch cluster solution is designed for deployments where latencies do not exceed 10 ms maximum round-trip time (RTT) between the zones containing data volumes. For Arbiter nodes follow the latency requirements specified for etcd, see Guidance for Red Hat OpenShift Container Platform Clusters - Deployments Spanning Multiple Sites(Data Centers/Regions). Contact Red Hat Customer Support if you are planning to deploy with higher latencies.
The following diagram shows the simplest deployment for a stretched cluster:
OpenShift nodes and OpenShift Data Foundation daemons
In the diagram the OpenShift Data Foundation monitor pod deployed in the Arbiter zone has a built-in tolerance for the master nodes. The diagram shows the master nodes in each Data Zone which are required for a highly available OpenShift Container Platform control plane. Also, it is important that the OpenShift Container Platform nodes in one of the zones have network connectivity with the OpenShift Container Platform nodes in the other two zones.
5.1. Requirements for enabling stretch cluster
- Ensure you have addressed OpenShift Container Platform requirements for deployments spanning multiple sites. For more information, see knowledgebase article on cluster deployments spanning multiple sites.
- Ensure that you have at least three OpenShift Container Platform master nodes in three different zones. One master node in each of the three zones.
- Ensure that you have at least four OpenShift Container Platform worker nodes evenly distributed across the two Data Zones.
- For stretch clusters on bare metall, use the SSD drive as the root drive for OpenShift Container Platform master nodes.
- Ensure that each node is pre-labeled with its zone label. For more information, see the Applying topology zone labels to OpenShift Container Platform node section.
- The stretch cluster solution is designed for deployments where latencies do not exceed 10 ms between zones. Contact Red Hat Customer Support if you are planning to deploy with higher latencies.
Flexible scaling and Arbiter both cannot be enabled at the same time as they have conflicting scaling logic. With Flexible scaling, you can add one node at a time to your OpenShift Data Foundation cluster. Whereas in an Arbiter cluster, you need to add at least one node in each of the two data zones.
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