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Appendix A: Introduction to SAS ● 60
SAS controller port options vary. A SAS controller with four phys could be configured with one
wide port, with two wide ports that comprise two phys, or with four narrow ports each
containing one phy. (A wide port with four phys is referred to as a 4-wide or 4x port.)
What’s a SAS Address?
Each SAS port is identified with a unique SAS address, which is shared by all phys on that port.
For example, a SAS disk drive might have two narrow ports. Each port has one unique SAS
address. The single phy in each port uses its port’s SAS address.
In another example, a SAS device might have one 4-wide port. That port has one SAS address,
which is shared by all four phys in the port.
Unlike SCSI devices and SCSI IDs, SAS devices self-configure their SAS addresses. User
intervention is not required to set SAS addresses, and SAS addresses cannot be modified.
What’s a SAS Connector?
A SAS or mini-SAS connector is the physical plug or receptacle that you see on a SAS device. It
supports the power and signal line cable. It’s what you plug a SAS cable into, or the end of the
SAS cable that’s being plugged in.
A connector is what forms physical links between phys. Some SAS connectors can support
multiple links. The number of links a SAS connector can support is referred to as its width.
Narrow connectors support a single link; wide connectors support up to four links.
A single SAS device may have one or more connectors. You can use a single SAS connector to
inter-link more than two SAS devices. For example, in the figure on page 59, the 4-wide
internal SAS connector forms links with four independent disk drives.
Mini-SAS connectors support both internal and external SAS connections. The mini-SAS
connectors are smaller than the standard SAS internal and external connectors. Mini-SAS
connectors support single and multilinks with the ability to scale to future speed needs.
What do SAS Cables Look Like?
Internal SAS cables are narrower than internal parallel SCSI cables. The connectors vary in size
depending on the number of links they support, from single link connectors to 4-wide (or
larger) connectors. Internal fan-out cables let you connect four disk drives to a single 4-wide
connector.
For an example of some internal SAS or mini-SAS cables and an external SAS cable, see
Selecting SAS Cables on page 28.
How are Disk Drives Identified in SAS?
In the BIOS and in the management utilities, disk drives are identified with numbers in this
format:
XX:YY:ZZ
where XX is the disk drive count number, YY is the enclosure number, and ZZ is the slot
number (within the enclosure). If the disk drive is not installed in an enclosure, a double
dashes (--) appear instead of YY and ZZ (for instance, 01:--:--).