In this PDF we describe the introduction of serial attached SCSI. We illustrate this using different points like SCSI, basic component of SAS, SAS protocol and topology etc. It is presented by http://www.shopricom.com/SG_XPCIE8SAS_E_Z

1. Introduction to the SAS
Serial attached SCSI is a method
used to access computer
peripheral devices. It employs the
digital data transfer over the thin
cable. In business enterprise it is
used to acess the mass storage
devices.

2. What is SCSI
SCSI is the acronym of small
computer system interface. It
defines a logical standard to
which disk devices must adhere.
This standard called common
command set. It is a type of
parallel bus.

3. Introduction to SCSI
This interface is a set of standerd
for physically connecting and
transfer of data between
peripheral devices.

4. Basic component of
SAS
1) Initiator.
2) Target.
3) Service delivary subsystem.
4) Expanders.

5. Initiator
It is a device that originate device
service and task management
system. It processing by the
target device. It is provided as on
board component in the
motherboard or as a host bus
adapter.

6. Target
A device containing logical unit
and target ports that receives
device service and task
management request. It could be
a hard disk or a disk array
system.

7. Service delivery
subsystem
It is a part of a I/O system that
transmit information between
initiator and target. Typecally
cable connecting beteen these
devices.

8. Expanders
It is a part of device delivary
system and faciliate connection
between SAS devices.

9. Example of SAS
There are many different types of
SAS. These are SFF 8482, SFF
8484, SG_XPCIE8SAS_E_Z etc.

10. SAS Protocol
SAS uses point to point
architecture that data between
two different SCSI devices. It uses
differential signaling for achieving
reliable and high speed
communication. It inherits it’s
command set from parallel SCSI
and uses full duplex
communication in the fibre
channel. It uses SAS 2 protocol
it’s link rate is 6.2 Gb/s.

11. Cables of SAS
SAS support active cables, those
are thin cables with active
circuitry to reduce cable weight
and management. Active circuitry
have build in driver, repeaters and
equalizing filter. It removes the ISI
(inter symbol interference), it is a
type of distorted signal. Driver
and repeater increased the signal
to noise ratio by up raising the
near end cross talk (NEXT).

12. Topology is a arrangement of
links, nodes or computers. It may
also be called as the structure of
network. LAN is a type of physical
topology. SAS has different types
of topology. Mainly internal and
external. There are lots of other
also.

13. Internal Topology
In this topology RAID system use
SAS or SATA drivers. Each drive
has point to point connection with
the controllers. Maximum eight
drives are supported by
controllers. A full height HP smart
expender card support eight
internal drives.

14. External Topology
In this type of topology the
controller connecting to the
external storage enclosure. Each
controller port incorporate four
lanes and total maximum
throughput 2400 MB/s. The
storage enclosure contains
internal 36 port expanders.

15. Multi Node Cluster
SAS using this topology it is an
alternative to the fibre channel
local loop topology. It gives you a
high availability with no point of
failure.

16. Dual Path Dual Domain
Architecture
T10 technological committee
SCSI defines as interconnection
of two or more SCSI devices.
When any part of data pathway
domains fails then data transfer
has stop because there is no
redundant pathway. But in this
architecture creates dual path
dual domain and redundant
pathway for storage.

17. Zoning
Zoning breaks topology into
different logical group for better
traffic management. It gives
unique ID in each expander PHY
to provide secure method for
managing SAS devices. All device
within zone group can interact
with each other.

18. SAS cable
SAS uses mini SAS 4X external
cable plug to connect to the end
devices with enclosure universal
port. Connector can attached with
the out of an enclosure or in port
of an enclosure. Connector have
icon to identify the type of
enclosure. It has a reverse key
allow them to accept SAS 2 cable
longer than 6 m.

19. Conclusion
SAS technology with different
signaling and active cable
continue to evolve and improve. If
you looking for high level
redundancy then dual domain
and dual path configuration helps
you. It increased the data
availability into the storage
network. Data availability is
essential for uninterrupted of
business operation.

20. THANK YOU