SAS address and port identifier.

Sheffield, Robert L robert.l.sheffield at
Thu Apr 27 08:51:43 PDT 2006

* From the T10 Reflector (t10 at, posted by:
* "Sheffield, Robert L" <robert.l.sheffield at>
It might help to think of a SAS address as a value that appears in a
particular format rather than an attribute of something. The text
describes four types of things that have SAS addresses, SAS initiator
devices, SAS target devices, SAS expander devices, and SAS ports. A SAS
device has one or more SAS ports. SAS device names and SAS port
identifiers both appear in the form of a SAS address, but they are not
the same thing, and, generally would have different values (though
that's not a requirement, and port identifers for expander devices are
always the same as the SAS address of the expander device itself).
If a device has multiple phys (e.g., a disk drive with two phys), there
are two ways those phys could be split into separate ports:
1 - each could have a unique SAS port identifier (i.e., the SAS address
reported by one phy would be different than the SAS address reported by
the other phy in the same device), or
2 - each phy could have the same SAS address, but be connected to
different SAS domains (i.e., the target ports of the SAS device would be
connected to different expander devices or different SAS initiator
What constitutes identification of a distinct SAS port is the
combination of SAS addresses (port identifiers) reported on either end
of a physical link. So, if four expander phys in the same SAS expander
device all connect to four phys of the same SAS initiator device, and
all four phys of the SAS initiator device report the same SAS address in
the SAS identify frame, then all four phys are part of the same SAS
port. However if two of the SAS phys in the SAS initiator device
reported one SAS address, and the other two phys reported a different
SAS address, that would constitute two distinct SAS initiator ports.
You can infer that because a SAS device has SAS ports, and SAS ports
have SAS addresses (serving as port identifiers), that implies,
indirectly, a SAS device has multiple SAS addresses, it's own "device
name", and the SAS addresses of the SAS ports that comprise the SAS
device. But only one of those SAS addresses may serve as the "device
name". So, even though a device can "have" multiple SAS addresses (by
virtue of its SAS ports having SAS addresses), it can only have one SAS
address that serves as a "device name". Any other SAS addresses is "has"
are port identifiers used by the SAS service delivery subsystem to route
OPEN address frames between SAS initiator ports and SAS target ports.
Hope this helps.
Bob Sheffield
Intel Corporation
-----Original Message-----
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Mona
Sent: Thursday, April 27, 2006 12:48 AM
To: t10 at
Cc: monika.talwar at
Subject: SAS address and port identifier.
* From the T10 Reflector (t10 at, posted by:
* Mona <monika.talwar at>
I am refrerring to version Working Draft Serial Attached SCSI - 2 
(SAS-2) [Project T10/1760-D(Reference number - ISO/IEC 14776-152:200x)]
I have some doubts regarding SAS address.
According to section 3.1.165
SAS address: A worldwide unique value assigned to a SAS initiator port, 
SAS target port, expander device, SAS initiator device, or SAS target 
Then in table-6 (page# 54) it says Port identifier is SAS address and 
Device name is SAS address.
Now on page#325,last line says 'More than one port in a SAS device may 
have the same SAS address'. This means that a device may have multiple 
SAS address in case it has multiple ports with different port 
identifiers. Then this voilates Section 3.1.165.
Please suggest where I am understanding it wrongly.
Best regards
Accelerating designs
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