Adaptec 2820SA User Guide - Page 62

What’s a SAS Port?, narrow port, wide port, width, Narrow

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Chapter A: Introduction to Serial Attached SCSI (SAS) ● 62 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 page 63), 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 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 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. 4-wide internal SAS connector SAS fan-out cable External SAS connector External SAS cable Single-port connector 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. A single SAS connector may help form links between more than two SAS devices. (For instance, as shown in the figure above, the 4wide internal SAS connector forms links with four independent disk drives.)

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Chapter A: Introduction to Serial Attached SCSI (SAS)
●
62
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
page 63
), 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 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 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. A single SAS connector may help form
links between more than two SAS devices. (For instance, as shown in the figure above, the 4-
wide internal SAS connector forms links with four independent disk drives.)
4-wide internal SAS connector
SAS fan-out cable
Single-port connector
External SAS cable
External SAS connector