Creating Remote Mirrors

Describes the use of remote mirror volumes. The remote mirror volume is present on a different cluster from the source volume.

Creating remote mirrors is similar to creating local mirrors, except that the mirror volume resides in a different cluster from the source volume. To properly identify the source volume, you must specify the source cluster name when the mirror volume is created. In addition, you must edit the mapr-clusters.conf file so that each cluster can resolve the nodes in the other cluster.

To create a mirror on a remote cluster, you must have the same UID for the MAPR_USER (the cluster owner) for both the primary cluster (where the source volume resides) and the remote clusters (where the mirror volumes reside; also known as the destination clusters). You also need to have the following volume permissions:

dump permission on the source volumes
restore permission on the mirror volumes at the destination clusters

When a mirror volume is created on a remote cluster (according to the entries in the mapr-clusters.conf file), the CLDB checks that the local volume exists in the local cluster. If both clusters are not set up and running, the remote mirror volume cannot be created.

To summarize:

Each cluster must be already set up and running.
Each cluster must have a unique name.
Every node in each cluster must be able to resolve all nodes in remote clusters, either through DNS or entries in /etc/hosts.
The UID for the MAPR_USER (cluster owner) must be the same for the source and destination clusters, irrespective of which user account triggers the mirror operation.
Volume permission must be set to dump on the source volumes.
Volume permission must be set to restore on the mirror volumes.