SAS address and physical location information

Many hardware error logs identify the location of a physical device, such as a SAS disk, using the unit address.

The unit address format is cceellFF, where:

• cc identifies the controller port to which the device, or device enclosure, is attached.
• ee is the expand port to which the device is attached. When a device is not connected to a SAS expander, for example, the device is directly connected, the expander port is set to zero.

Generally, the range of the expander port is 00 to 3F hex. A value greater than 3F indicates there are two expanders (for example, cascaded expanders) between the controller and device. For example, a device connected through a single expander might show an expander port of 1A, while a device connected through a cascaded expander might show an expander port of 5A (that is, a value of 40 hex added to the expander port indicates the presence of a cascaded expander), but in both cases, the device is connected off port 1A of the expander.

A value of FF indicates the expander port is not known.

• ll is the logical unit number (LUN) of the device.

A value of FF indicates the LUN is not known.

A resource can identify a physical device or it can identify other SAS components. For example:

• FFFFFFFF indicates the identity of the device is not known or indicates a SAS RAID controller.
• ccFFFFFF identifies only a controller SAS port.
• cceellFF identifies the controller port, expander port, and LUN of an attached device.

Figure 1. Example of SAS subsystem unit addresses

The following figure depicts the unit addresses for the CCIN 57CD PCIe SAS RAID and SSD Adapter.

Note: Each of the integrated SSDs is directly connected and thus the expander port is equal to zero in the unit address. Also, the LUN of each device is zero.

Figure 2. SAS unit addresses for CCIN 57CD PCIe SAS RAID and SSD Adapter 3 Gb x8