Local Mirroring

Describes the use of local mirror volumes. The local mirror volume and its source are present on the same cluster,

A local mirror volume is a mirror volume whose source is on the same cluster. Local mirror volumes are useful for load balancing or for providing a read-only copy of a data set.

You can locate your local mirror volumes in specific servers or on racks with particularly high bandwidth, mounted in a public directory separate from the source volume.

The most frequently accessed volumes in a cluster are likely to be the root volume and its immediate children. To load-balance read operations on these volumes, mirror the root volume (typically mapr.cluster.root, which is mounted at /). By mirroring these volumes, you can serve read requests from the mirrors, and distribute load across the nodes. Less-frequently accessed volumes that are lower in the hierarchy do not need mirror volumes. Since the mount paths for those volumes are not mirrored throughout, those volumes are writable.

NOTE
If you are creating a local mirror of the root volume, root(/) points to the mirror volume, hence root is read-only. For read-write copy of root (/), you must use the special path, /.rw