SnapMirror creates either asynchronous or synchronous replicas of volumes that host LUNs.
With asynchronous SnapMirror, data is replicated from a source volume to a partner destination volume at regular intervals.
With synchronous SnapMirror, data from a source volume or qtree is replicated on a destination volume or qtree at, or near, the same time it is written to the first storage system.
When the LUN data on your source volume is offline or no longer valid, you can connect to and use the copy of the LUN on the SnapMirror destination volume. Unless otherwise indicated, the information discussed in this chapter applies to volumes that host SnapMirror LUNs, whether they are asynchronous or synchronous.
If a storage system volume or storage system holding one or more LUNs suffers a catastrophic failure, you can use a mirrored destination volume to recover the LUNs.