MPC-3900 Is No Longer Available
The MPC-3900 comes with 6 drive bays that support SATA hard drives. Each SATA hard drive is installed in a removable tray. The drive cage shown in these images includes four SATA hard drive bays.
The enlarged image show three of the trays in the closed (connected) position, and one being disengaged, by pulling out the lever to eject the tray.
The last image shows the drive cage with all trays removed. The SATA hard drive data and power connectors are indicated by (1).
You install/remove a hard drive by simply inserting/extracting the removable tray. No more hassles with cabling the hard drive to the motherboard.