There is considerable confusion around the need for HOST or TARGET specific SFF-8484 cables, and also a lack of reliable information about how to identify which cable is which. We sell both types of cable, and many associated SATA/SAS accessories in our eBay Store, so we wrote this guide to help our customers determine the best cable for their needs, and as a guide to identifying cables that they might already have.
SFF-8484 ports are commonly referred to as SAS, SAS32, Internal Multilane or Internal 4-lane ports, and should not be confused with the smaller, internal Mini-SAS ports (SFF-8087), or external Multilane ports (SFF-8470) or the smaller, external Mini-SAS ports (SFF-8088).
SFF-8484 ports have 32 pins, and a polarising feature that prevents a cable from being inserted incorrectly. The 32 pins are capable of transferring data for up to 4 devices (hence 4 lanes), and additionally, can optionally provide extra signals on a sideband cable (sideband signals are beyond the scope of this review). A SFF-8484 cable does not carry power for the attached host or target devices, although some fanout cables do allow power to be supplied to the SATA device via an additional molex input connector.
Internal Multilane (SFF-8484) ports can be connected to up to 4 SATA ports, using a SAS-to-SATA fanout cable. There are 2 different wirings, depending upon whether the SFF-8484 port is on the HOST device or the TARGET device.
Which devices have SFF-8484 ports?
SFF-8484 ports are most commonly found on SAS controllers, and those controllers are most commonly found installed in a PCI or PCI-Express slot. However, SFF-8484 ports can also be found on backplane boards, and on some disk enclosures. SATA ports can be found on many consumer-grade SATA controllers, on many disk enclosures and also on SATA hard drives and SATA optical drives.
HOST vs TARGET
A SATA or SAS controller is widely referred to as the HOST device, while the connected devices are known as the TARGET devices. Put another way, the HOST controller is hosting the connected devices, and when the controller needs to signal one of the devices, it targets that device.
A SATA HOST controller that has SATA ports can connect to SATA devices using ordinary SATA cables, and it does not matter which end of the SATA cable is connected to the HOST, nor which end is connected to the TARGET device. The same is not true, however, when connecting a SFF-8484 fanout cable between a SFF-8484 device and SATA devices - It is essential that either a HOST based SFF-8484 fanout cable or a TARGET based SFF-8484 cable is used, as dictated by the hardware in use.
HOST SFF-8484 to SATA Fanout Cables
A Host based SFF-8484 - SATA fanout cable has the SFF-8484 connector attached to the SFF-8484 HOST device (most commonly a SAS controller), and the SATA connectors connected to the SATA/SAS devices (most commonly SATA or SAS hard-drives). It is common to connect a HOST based cable between a SFF-8484 host controller and the rear of a SATA/SAS disk enclosure (the enclosure then passes the signal to the target devices inside the enclosure)
TARGET SFF-8484 to SATA Fanout Cables
A Target Based SFF-8484 - SATA fanout cable has the SATA connectors attached to the HOST device, and the SFF-8484 connector attached to a SFF-8484 port on a target device. An example would be connecting 4 ports from a SATA controller to a single SFF-8484 port on a backplane-board.
How to Identify HOST and TARGET SFF-8484 Fanout Cables
At first glance, HOST based and TARGET based cables are virtually idential. Some have markings or labels that can assist (HOST based cables in our eBay Store have labels attached), but many do not, so identifying the HOST/TARGET bias of a cable can be very difficult.
We've created some pictures to help you determine whether the SFF-8484 connector is HOST or TARGET based. For this example, we've used 2 SATA connectors with latches, and 2 SATA connectors without latches, so you can compare to the SATA connectors in use on your cable. A regular fanout cable will have all latched or all non-latched SATA connectors.
As you can see below, the difference is very subtle. Both use the same SFF-8484 and SATA connectors and cabling, the only difference is the wiring, but thankfully there is one identifying feature, thanks to the position of the L-Shaped polarizing features on the SFF-8484 connector, in relation to the L-Shaped polarizing feature on the SATA connectors.
It is necessary to look at the position of the L-Shaped notches on both ends of the cable. The following diagrams explain in more detail...
SFF-8484 (Host) - 4x SATA
The HOST based wiring has the L-shaped notches on all connectors, on the same side of the cable, and when the SATA L-shaped notches are pointing down, the SFF-8484 connector L-shaped notch will be pointing up.
SFF-8484 (Target) - SATA Fanout Cable
The TARGET based wiring has the L-shaped notches on the SFF-8484 connector, on the opposite side of the cable to the SATA connectors' L-shaped notches, and when the SATA L-shaped notches are pointing down, the SFF-8484 connector L-shaped notch will be pointing down.
If you need SFF-8484 - SATA fanout cables, be sure to visit our eBay Store