Dell Studio 1558 (Early 2010) - Manual (Page 317)

Ports
317
eSATA Port
SATA (Serial Advanced Technology Attachment) is a computer bus primarily
designed for transfer of data between a computer and mass storage devices
such as hard disk drives and optical drives.
External SATA or eSATA, users can now utilize shielded cable lengths up to 2
meters outside the PC to take advantage of the benefits the SATA interface
brings to storage. eSATA provides more performance than existing solutions
(up to 6 times faster than existing external storage solutions: USB 2.0, &
1394) and is hot pluggable.
eSATA is commonly used for External Direct Attached Storage for notebooks,
desktop, consumer electronics and entry servers.
Pin Signal
1 GND
2 DR+
3 DR-
4 GND
5 DT+
6 DT-
7 GND