6.2 General Requirements for Geo-replication

Geo-replication requires at least two gluster clusters to be configured to the level where a volume is accessible on each cluster. One cluster is treated as the master cluster, and the second is treated as the slave. The master cluster may already be in use prior to the configuration of a slave cluster.

Clusters must be set up and configured following the requirements set out in Chapter 2, Installing Gluster Storage for Oracle Linux. Notably, all nodes in both clusters must have network synchronized time using an NTP service, such as chrony.

Geo-replication is performed over SSH between the master cluster and the slave cluster. The two clusters should be able to connect to each other via SSH. Access should be available for all nodes in all clusters that take part in geo-replication, so that failover between nodes is handled appropriately. Networking and firewall configuration must facilitate this.

Ensure that the slave cluster volume that you are using for mirroring is clean of data and that it has sufficient capacity to mirror the content on the master cluster.

Install the glusterfs-geo-replication package on all nodes in both clusters. For example:

$ sudo yum install glusterfs-geo-replication

Other general software requirements are met by default on most Oracle Linux systems, but you should check that you have the latest available versions of:

  • rsync

  • openssh

  • glusterfs

  • glusterfs-fuse

Important

When using geo-replication in conjunction with the Gluster snapshot functionality, you must ensure that snapshots should not be out of order on master and slave nodes on restore. Therefore, when taking a snapshot of a volume on master node, pause geo-replication first and take a snapshot on both the master node and on all slave nodes, before resuming geo-replication. Equally, when restoring from a snapshot, pause the geo-replication, and perform the restore on all nodes before resuming geo-replication.