There are several variations possible while deploying SnapMirror. These variations allow you to customize the solution to suit your requirements.
Source to destination to tape variation: A common variation to the basic SnapMirror backup deployment adds a tape backup of the destination volume. By running a tape backup off the SnapMirror destination volume (as shown in the following illustration), you do not subject the heavily-accessed source volume to the performance degradation and complexity of a direct tape backup.
Source to tape to destination variation: A SnapMirror deployment that supports SnapMirror replication over low-bandwidth connections accommodates an initial mirroring between a source and destination volume using physically-transported tape (as shown in the following illustration). After the large base Snapshot copy has been replicated, smaller, incremental Snapshot copy updates can be carried out over a low-bandwidth connection.
Cascading destinations variation: A variation on the basic SnapMirror deployment and function involves a writable source volume replicated to multiple read-only destinations. The function of this deployment is to make a uniform set of data available on a read-only basis to users from various locations throughout a network and to allow for updating that data uniformly at regular intervals.
In a qtree SnapMirror relationship, the resync operation from the destination qtree to the source qtree fails if the source qtree is busy updating another destination qtree. For example, you have qtree SnapMirror relationships from qtree A to qtree B and from qtree A to qtree C. If you try to perform SnapMirror resync from qtree B to qtree A when qtree A is busy updating qtree C, the resync operation fails.