Can I add internal drives into 847 chassis (6047R-E1R36N, 847E16, 847E26)
Yes, you will need MCP-220-84701-0N (internal drive tray for 1x 3.5" HDD or 2x 2.5" HDD) and a SATA cable (size depends on motherboard, around 70CM to be safe, CBL-208L). The power for the drives will come directly from the Power Distibutor board.