optimal architecture for database

In real time all the database files are placed in same disk or different disks? 
and what is the optimal positions for controlfiles,redologfiles. datafiles, 
Is RAID technology is used?

In a modern datacenter today, you'll find that you have very limited options of 
storage solutions for ORACLE -- most of the time you'll be running on some form 
of RAID-5 implemented by the storage vendor.  And it's for a good reason -- 
storage these days is fast due to hardware write/read cache so what we used to 
do back in 1996 is no longer needed.  Having said that I am from the old school 
and prefer RAID-10 for ORACLE datafiles and REDO logs.  ORACLE_HOME and Control 
files can go on RAID-5.