The DS220+ expands via eSATA to 5 more bays
One eSATA port connects a DX517 expansion unit (up to 5 additional drives), and there are two USB 3.0 ports for external drives or peripherals.
One eSATA port connects a DX517 expansion unit (up to 5 additional drives), and there are two USB 3.0 ports for external drives or peripherals.