Mirror copies of redo logs I'm running an two node RAC database with ASM having two DGs one for data and one for redo. I have only one copy of redo and I have the need to have another copy of redo logs.
1. How to go ahead with adding mirror copies of redo? 
2. Will it demand downtime? 
3. Can I add the copies which I'm going to create in the data DG?
4. I also need to create a copy for the control file. How can I do that as well?

Thanks,
Tesla.
You won't need downtime just to add additional redo logs to your redo groups.

Take a look at this:

Oracle Configuration Best Practices

And then look at this:

Creating Redo Log Groups and Members

You will need downtime to add additional control files:

Creating Additional Copies, Renaming, and Relocating Control Files