The Fujitsu Futro S900 was built up to 2013, and only had one SATA port from the factory. [Jan] wanted to add another as this would make the device more useful as a network attached storage server.

For example, an eSATA port multiplier allows multiple external SATA drives to be connected to one eSATA port on the computer. Also called a "port expander," another example is a USB hub ...