Diskgroups for redo, controlfiles, and temp?

Has anyone ever run into blogs that have demostrated large performance gains, when on a SAN, by splitting out redo, controlfiles, and temp onto their own diskgroups? I don't recall ever seeing this as a best practice and in this periodic discussion brought up to our group I believe has agreed. I'm getting pressure from an outside resource to split out these file types for performance reasons yet haven't received anything specific to explain why and the arguments presented have been high level and similar to arguments from long ago on older hardware.

Dave Herring

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