Microsemi Adaptec ASR-8405E - Whats a Phy; Whats a SAS Port; Whats a SAS Address

Wide
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Phy
Receiver
Transmitter
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Narrow
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Transmitter Narrow
Port
SAS DeviceSAS Device
SAS Device
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SAS Device
link
A.4 What’s a Phy?
Phys are part of the physical communication connection between SAS devices. Each phy contains a transceiver
that sends data back and forth between SAS devices.
When a connection is formed between two end devices, a link is established from a phy in one port to a
phy in the other port. As shown in the gure above, a wide port can support multiple independent links
simultaneously.
Phys are internal, within SAS connectors (see What’s a SAS Connector?SAS connectors).
SAS cables physically connect one or more phys on one SAS device to one or more phys on another SAS
device.
A.5 What’s a SAS Port?
Note: Because the physical link between SAS devices is from phy to phy, rather than port
to port, a “port” is more of a virtual concept, different from what is normally considered
a port on other types of RAID controllers and storage devices.
A port is one or more phys. A narrow port contains one phy. A wide port typically contains four phys.
Each port has its own unique SAS address (see How are Disk Drives Identied in SAS? SAS disk drive
identiersdisk drives SAS identiersdisk drivesSAS disk drives), and all the phys in a port share that same
SAS address.
SAS card port options vary. A SAS card with four phys could be congured 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.)
A.6 What’s a SAS Address?
Each SAS port is identied 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.
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Microsemi Proprietary and Condential. Installation and User's Guide Revision 5
Introduction to SAS