Asus RS704DA-E6/PS4 - Manual (Page 68)

4-18 Chapter 2: Hardware information
10. HDD status indicator header (9-1 pin HSATAT1)
This connector is for the indicators at the back panel. The indicator lights up
when the corresponding SATA hard disk functions abnormally.
11. Hard disk activity LED connector (4-pin HDLED1)
This connector is used to connect to a hard disk drive active LED connector
on the SCSI or RAID card.