1. What does it mean Backup and Test the backup can be restored?

"Make sure anything that could be affected by what you are about to do can be fully recovered from if the worst happens" That includes recovering the OS, the OS configuration, the cluster configuration (if one node is OK you have a backup of the cluster config because all nodes share the CIB). Then there is the data, if this is on a SAN it will have its own dedicated backup procedure so work with the storage team.

2. Is there any script to make backup? Is there any script to restore the cluster based on backup?

The term "backup" is interesting because there are many different components, OS, OS configuration, cluster configuration, the data. We recommend investigating REAR, Relax and Recover - See the documentation, Section 24:- https://www.suse.com/documentation/s...ook_sleha.html

3. Or is the process completely manual?

This process can be automated

4. What are the best practices to backup a cluster?

We do not have a best practices for back ups.