I have always multiplexed my online redo log files and control files in all Oracle databases that I manage. I typically use Disk mirror method EXTERNAL when I create disk groups in an ASM instance because I know the disks are on a RAID SAN disk subsystem. However, I wanted to get other's thoughts on this. Is file multiplexing and ASM mirroring still necessary with RAID? ASM has some great failgroup configuration features and mirroring capabilities but is it overkill or just flat out unncessary in a RAID environment? I guess the higher level question would be, is software mirroring necessary when your disks are in a RAID subsystem? I would imagine yes because it doesn't protect against someone deleting a redo log file, etc..
Please let me know your thoughts?
Thanks,
--Justin