Asus RS300-E8-RS4 - Manual (Page 57)

ASUS RS300-E8 Series 4-9
3. Hard disk activity LED connector (4-pin HDLED1)
This LED connector is for the storage add-on card cable connected to
the SATA or SAS add-on card. The read or write activities of any device
connected to the SATA or SAS add-on card causes the front panel LED to
light up.
4. USB 2.0 connector (10-1 pin USB78; A-Type USB9)
These connectors are for USB 2.0 ports. Connect the USB module cables to
these connectors. These USB connectors comply with USB 2.0 specification
that supports up to 480 Mbps connection speed.