Backup DB from Exadata to ZFS Backup Appliance

If you think about RMAN performance and your hardware is of high level or
if you will backup database from Exadata to the ZFS Storage Appliance 
                                  then look here :

• For backup to backupset and restore from backupset:
• _backup_disk_bufcnt=64
• _backup_disk_bufsz=4194304
• For image copy backup and restore:
• _backup_file_bufcnt=64
• _backup_file_bufsz=4194304

And references:

Configuring Oracle RMAN and the Oracle Database Instance: http://docs.oracle.com/cd/E28223_01/html/E27586/configappl.html  

MOS Note:  1072545.1: RMAN Performance Tuning Using Buffer Memory Parameters. 

And the nice presentation how to marriage the ZFSSA and Exadata: http://www.dbaexpert.com/DOUG%20Exadata%20with%20ZFS%20Storage%20Appliance.pdf