I'm not aware of anyone using DBFS for backup staging.
A few reasons I can think of: DBFS is fundamentally a block filesystem on top of SecureFiles objects on a database instance. In a failure scenario affecting the DBFS instance, where would you stage backups to restore from? Additionally, the default Exadata DBFS diskgroup is not configured for maximum performance, as it doesn't span all storage servers.
The more standard approach would be to use your FRA for disk-based backups and use a RMAN media manager to send backups to tape.
Oracle recommends FRA for rman backup.
Use the following methods in Oracle Exadata for rman:
1. Incremental backup performance is improved. Because Block filtering is offloaded to Exadata Storage Server and enable block change tracking also
2. Fewer blocks needed to be processed by rman not all
3. Offload processing in Exadata Storage Server is automatic and transparent to the user.
4. EHCC also will help for improving rman backup performance.
Hope it helps...
Yes. you can use DBFS for RMAN backups. However the best practice is to use FRA (on ASM) to make your disks backups.
For Tape backups Oracle recommends a Media Server with OSB (or another softw for tape backup).
You can do your RMAN Backups on DBFS, however you cannot share then (NFS) from DBFS. You can use dbfs_client or commom scp tp copy from Exadata to your network.
Just to remmeber: DBFS is a Database inside ASM, so performance would not be fast as FRA.
As others have pointed out already, DBFS is (even if it should be supported) a bad idea for RMAN backups.
On Exadata, if you want to use the space of the DBFS_DG diskgroup for RMAN backups - just backup directly into it.
Something like backup database format '+DBFS_DG';
There is no need to use the DBFS filesystem for that.
"Don't believe it, test it!"