best (reliability required, best speed at lowest resource consumption still important) way to get ASM contents to a file system for non-plugin tape jobs?

If anyone has measured performance and tested reliability of copying ASM contained files onto a file system, I'm all ears.  

So far I have considered the cp command of the asmcmd utility and the DBSM_FILE_TRANSFER.COPY_FILE package.  

For the purposes of this exercise, we can assume that the ASM contained files to be copied are quiescent.  

I'm also interested in any "lessons learned" attempting such copies, and suggestions for alternatives within the scope of starting from ASM and landing on regular file systems.  

This is to get generations of integral backups out of the an ASM based FRA onto disk, which as far as I can tell is not something RMAN actually does.  

If I've missed the memo on how to do that, please advise, but all I see is going to SBT_TAPE for that.  

Regards, and thanks in advance,  

mwf  

PS: Repeating the RMAN backups directly to a file system (repeating the rdbms load of backup and the i/o and cpu load) has been considered and we're looking for something better than that. (But the scope remains ASM to file system.)

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