Wide Scsi
2009
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Wide Scsi
SAS Technology
SAS Technology
1. What is SAS
SAS – Serial Attached SCSI, A natural transition from parallel SCSI to serial
2. Why Serialize?
Signal skew and crosstalk; Signal termination restrictions; Cable and connector reflections;
Device addressability
3. SAS Performance
3.0Gbps(300MB/s)per single SAS port; Port Aggregation, eg. Combine 4 ports to a single
12Gbps WIDE PORT (x4 port); Full Duplex (24 Gbps); Multiple Initiators and Targets (with
Expander); Advanced Command Queuing
4. SAS Features/Benefits
Flexibility (Coexist of SAS and SATA Drives; SCSI software/middleware can be used);
Scalability (Up to 16,256 SAS/SATA devices in one SAS Domain; Expander is able to
connect 128 devices); Reliability (Dual Port and Multi-initiator for Fault Tolerance; Hotswap
connector; High MTBF Drive)
5. Advantage of SAS Interface
High Speed Serial SCSI instead of Parallel; Point-to-Point Connection; Expander for
Scalability; Dual Port Connectivity; SATA Compatible Dual 7-pin Interface; Port
Aggregation e.g. x4 WIDE PORT
6. What is a SAS Expander?
SAS devices:
(1)end devices:
SAS initiator devices (hosts), SAS target devices (peripheral devices) , and SATA devices
(2) expander devices:
edge expanders (sets), and fan-out expanders
Expander devices are the intermediary devices that allow more than one initiator to have a
connection to more than one target.
7. Interface Comparison
ATA SATA SCSI SAS FC
Interface Parallel Serial Parallel Serial Serial
Addressing 2 1 or 16 w/ SATAII 16 128 16 million
Connection 80-pin 7-pin 68-pin 7-pin Copper/optical
Dual-port No No No Yes Yes
Duplex Half Half Half Full Full
Cable length 0.4m 1m 12m 10m 30m(copper)300m(optical)
8. Maximum devices that can connect to SAS
16,256 with expanders
9. SAS appliaction
Midrange and enterprise servers
10. SAS topology
Point-to-point w/ expanders
About the Author
HP HD 18.2GB HS Ultra3 Wide SCSI HD 15k Festplatte
