can anyone tell me how to make a backup or where to find doc of the exadata machine's configuration when one has configured the machine with all the networks etc.
> can anyone tell me how to make a backup of the exadata machine's configuration
The backup of OS only needs to be done for the db nodes. You can ask a backup admin (hope you have one) to implement a backup similar as other linux OS backups.
use RMAN as a common database.
Inside CELL if you choose "Normal Redundancy" you can recover disks without problems.