User can find the S/N on the WebUI as the follow, Dashboard => Device information => Serial number, or from the S/N label on the chassis.
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, users can enable multiple share types in the same file system. Such as, CIFS, NFS, FTP, AFP. 
No, you don't. Pre-installation is not needed for all Qsan NAS products. Simply install the unit and link to your client host, then login to webui via default IP address: to setup the unit if an DHCP IP didn't be given to the management port.
Yes, U300-F30 supports LUN masking.
Yes, Qsan Rsync is SSH encrypted.
No, only users can access to his own folder. (There is no path for admin to access other userhome folders.)
Yes, Qsan NAS products are designed to tolerate at least one PSU failure (for two PSUs system)/two PSUs failure (for three PSUs system) in the system. However running the system with one PSU for a long time is NOT recommended.If any PSU fails, please contact Qsan reseller for replacement as soon as possible.
No, Rsync doesn’t provide iSCSI/FC volume backup service. It only can be used in the filesystem.
The follows is the matrix of Qsan NAS product support disks:
SATAOOOO(with Mux board)O(with Mux board)