A snapshot is a read-only connection of a file system or volume at a given point in time. Based on ZFS technology, a snapshot can be taken instantly without taking up too much CPU resource.
The volume snapshots will be stored in the pool, but user needs to be careful the snapshot usage of the pool capacity. And filesystem will be stored in the share foler as hidden folder, so it may produce so many invisible folders under the root share folder.
The max number of U2/U3/U4/U6 is 4096. U1 is 2048.  
Yes, user can delete one snapshot alone, it won't be caused any issues. There is no dependencies for delete actions.
A clone is an writable connection of a volume or a file system, and it only can be created from the snapshot.
But the clone will be deleted together when the snapshot is created from is deleted.
The clone task will be deleted together when the origin snapshot had been deleted.
It is a kind of backup feature. When user starts to do Rsync, the backup data will transfer from client site(source) to server site(target). And Qsan Rsync feature is different with Qreplica, Rsync can backup file by the selected path, and Qrelica only can bakcup all volume/Filesystem. Moreover, if the server or other brand NAS has the Rsync feature, our NAS can do Rsync with them, too. And Qsan Rsync is designed to divide into two mode - server mode and client mode. It would be more compatible.                
Yes, Qsan Rsync is SSH encrypted.
No, Rsync doesn’t provide iSCSI/FC volume backup service. It only can be used in the filesystem.
1.If users want to do Rsync as the server site(target), users must be enable the Rsync server first.
2.After enabling Rsync server, users need to create a target module. If users don't create it, the client site can find the server site to do Rsync function.
3.After creating the target module, user can find the target module when doing Rsync from client site to server site.