Yes, the system will do the full copy upon first time execution of the task. Afterwards the replication will be carried out in incremental manner.
The replication feature basically works on snapshot bases, every time a replicatoin task is executed, a snapshot is taken on the source zfs and then sent to the destination zfs. The zfs replication mechanism automatically checks and compares the snapshot versions between the source and destination to make sure the snapshots are identical and via comparison between the snpashots, decides which incremental data needs to be sent.
No, for using the replication feature you don't need a license to activate it. The feature is directly configurable in the Web UI -> Service configuration > Backup > Replication.
You can create up to 16 tasks for all Qsan NAS models except only 8 for U1 series.
No, it's file level feature. So if the task fail please try to do the task again.
Yes, if the Rsync job had been ever stopped, just restart the job, and then it will verify the backup file with two sites. The file that didn't backup will continue to Rsync process.
On U1 series, the maximum of Rsync tasks/targets are 8/4. On U2/U3/U4/U6 series, the maximum of Rsync tasks/targets are 16/8.