Clusters are widely used with respect to the criticality of the data or content handled and the processing speed expected. Cluster requires a minimum of two servers - the connected servers execute operations all together thus creating the impression like a single system. If one server in a cluster fails, the other server(s) in the cluster can pick up the workload. This prevents the loss of valuable time and information if a server fails.
For a business critical system like SAP, whether system hosted in on-premise or in the cloud - cluster is used to increase resource availability. One can configure the high availability for the database resources or database and application resources - depending upon the business need. Pacemaker is an open source cluster resource manager (CRM), a system that coordinates resources and services that are managed and made highly available by a cluster. Pacemaker is used on computer clusters since 2004. It implements several APIs for controlling resources, but its preferred API for this purpose is the Open Cluster Framework resource agent API.
The following document describes the steps for "Setting up Pacemaker on SUSE Linux Enterprise Server in Azure".
There are two options to set up a Pacemaker cluster in Azure.
One can either
- use a fencing agent, which takes care of restarting a failed node via the Azure APIs
or
- use an SBD device, Storage-Based Death(SBD) allows Pacemaker to use a watchdog device to halt a node. While its name derives from using shared storage for coordination, only a watchdog is required - shared storage is optional.
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