Mirror Cascades

In a cascade, one mirror synchronizes to the source volume, and each successive mirror uses a previous mirror as its source. Mirror cascades are useful for propagating data over a distance, then re-propagating the data locally instead of transferring the same data remotely again for each copy of the mirror. In the example below, the < character indicates a mirror's source:

/ < mirror1 < mirror2 < mirror3

A mirror cascade makes more efficient use of your cluster's network bandwidth, but synchronization can be slower to propagate through the chain. For cases where synchronization of mirrors is a higher priority than network bandwidth optimization, make each mirror read directly from the source volume:

mirror1 >   < mirror2
          /  
mirror3 >   < mirror4
You can:
  • Create a mirror cascade by setting the source volume of each mirror in the Properties tab of the MapR Control System when creating a mirror volume.
  • Break a mirror cascade made from existing mirror volumes by changing the source volume of each mirror in the Properties tab of the MapR Control System when editing the mirror volume.