First, the Red is a poor choice for a server. Second, you need RAID drivers loaded in order to see the RAID array to install to.  Which RAID controller are you using? Third, if you are using a single 3x4TB=8TB RAID 5: Alternatives:  
Hello guy! I have a Server Dell PowerEdge T620 I did a Raid 5 for 3 Hard disk drive WD30EFRX Red drive ( each 4TB)When I'm installing Windows Server 2008, not find hard disk, which make installation. someone help me? Thanks in advance
Problem during installing Windows Server 2008 at my Server dell