raid on emc

Hi Gurus and Mr.Kagel, This subject discussed many times before : raid 5 versus raid 10 or 01 . The story is same , the question is same but i am little bit confused . This is Oracle related , but i am new with oracle , but experienced with informix , thats why i send it here. I am setting up a large datawarehouse on Oracle RAC with Emc disk array. The emc site suggest to use raid 5 , i want to use raid 10 or 01 because of the points that were discussed on this forum . Since the system is datawarehouse and dss type , i will have no write . So if i use raid 5 , i will have no write performance problem. (Right?) What is the performance benefit of raid 10 against raid 5 ? And , the disk crashes problem : If one disk fails , raid 5 is ok , if two fail , it is hell. If we think the emc box , do i have to consider such a problem ? Kind Regards, hope