I guess this question is somewhat to wide and not enough information is specified.
What are you planning to use, how many users, how do you envision you HA config,...... what is your budget.
I want to install R12.0.1 E-Biz with 10g DB, Please let me know best Hardware available(configuration cpu,memory etc) for high availability for Linux OS.
Any reason you are installing 12.0.4 and not 12.1.1?
For the hardware specs, please see the installation manual and the old threads since this topic was discussed many times in the forum before.