Please see page 202 of this document:  [URL]  You can have a Synchronization policy where it is possible to fail over and fail back between source and target clusters.  As well you can also configure a Copy policy, where if you delete files on the source cluster, the copied file on the target cluster is not deleted.  Copy policies are used primarily for archival purposes. 
We upgrade isilon code version to 7.1 which has continuous sync IQ feature.   Question:   Could some please answer,  If we delete files on source directory does it reflects on Target directory as well ( files get deleted from target ?)  ?
Isilon Sync IQ