There's a chapter in the ePO installation guide about cluster installation you should review which will cover the basics.
I guess the two biggest take-home points would be:
1. Microsoft Cluster Server supported.
2. Cluster installation requires you to use a manually installed a SQL Server on a system other than where you install your ePolicy Orchestrator software.
What do you mean by manually installed SQL Server?
Providing SA DB user during the ePO installation doesnt work?
Manually installed means an Sql instance not installed by ePO directly but using the Microsoft SQL Installer.
Understood!! Thanks Pal!