1. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 1 SAS Technology Auteur : Franck THOMAS

2. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 2 Introduction  SAS is not something entirely new, but it merges the best of two worlds.  The first part is the serialized transmission of data, which requires far fewer physical connections. Moving from parallel to serialized operations has eliminated the use of a bus as well. Although the current SAS specification defines a 300 MB/s bandwidth per port, which is less than UltraSCSI's 320 MB/s, exchanging the shared bus by point-to-point connections between devices is a huge advantage.  The second important ingredient for SAS is the SCSI protocol, which is popular and powerful.

3. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 3 SATA Cables & Connectors – internal  SATA 1 and SATA 2 was defined for internal use only (e.g. inside a PC)  1 m internal cable  SATA I 1.5Gb/s  SATA II 3Gb/s Fix Configuration Hot Swap Configuration

4. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 4 SAS Cables & Connectors – internal  Similarly, SAS defines internal environments  Backplanes support two physical links (dual port)  Cables mainly support one phy  SAS 1: 3Gb/s The signalling equals to what is used in SATA. Source: Adaptec. Hot Swap Configuration Fix Configuration

5. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 5 SAS / SATA HDD different connectors SAS and SATA HDD connectors  No Notch Dual Port  SATA backplane connectors will NOT accept SAS HDDs  SAS backplane connectors accept both SAS and SATA HDDs

6. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 6 Cabling 1/2 Internal PortsPictureExternal PortsPicture Single port name ? SAS/SATA (1 x 3Gb/s) e-SATA Only for SATA HDD Single port + power SFF-8482 SAS/SATA (1 x 3Gb/s) N/A 4 ports * SFF-8484 SAS/SATA (4 x 3Gb/s) 4 ports * SFF-8470 SAS/SATA (4 x 3Gb/s) 4 ports * SFF-8087 SAS/SATA (miniSAS) 4 ports * SFF-8088 SAS/SATA * 4 ports cables are also called « multi-lane »Only connector on cable side is represented (not on controller side)

7. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 7 Cabling 2/2 SFF-8484 : multi-lane internal cable to link host adapter to backplane SFF-8482 : connector to link a drive to a single SAS port

8. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 8 SAS Protocols 1/2  SSP - Serial SCSI Protocol  Used whenever SAS HDD talks to SAS Controller (with or without SAS Expanders)  SATA  Always used to communicate with a SATA HDD  STP - SATA Tunnelled Protocol  Used when SATA HDD is connected to SAS controller via SAS expander  STP is used between SAS controller and SAS expander; SATA is used to talk to the SATA HDD  STP EMB (Enclosure Management Bridge), Allows a SAS controller to talk to the I2C interface embedded in the x12 Expander. Typically the I2C interface is connected to an external Enclosure Management Processor  SMP - Serial Management Protocol  Allows SAS controllers to configure SAS expanders

9. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 9 SAS Protocols 2/2 SAS HDD SATA HDD SATA HDD SAS Controller SSP STP SATA SMP SATA Enc. Proc I2C bus SAS Expander SSP SAS HDD SSP SAS Expander STP EMB

10. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 10 SAS Expander example for external cabling SAS Expander allows cumulative bandwidth on several ports (aggregation) and acts like a hub (more devices than ports):  Combine ports: 2 ports = 6Gb/s, 4 ports = 12Gb/s, … Host with 4 ports SAS controller External SAS Disk Attached Storage with 8 disks 4 line cable 4 x 3Gb/s SMP/SSP/STP

11. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 11 SAS external connections This is a SFF-8470 cable for external multi-lane SAS links.

12. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 12 SAS Address - WWN A 60-bit field containing a 24-bit company identifier and a 36-bit uniquely assigned by that company WorldwideName (WWN) – Unique address 00000000_00000000h represents invalid address Each SAS device has a different WWN

13. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 13 Management / Monitoring SGPIO management bus can be routed on separate cable or encapsulated on SAS physical layer (STP EMB)

14. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 14 Comparison of SATA, SAS, and Fibre Serial ATASerial Attached SCSIFibre Channel AL Performance Half-duplex Full-duplex with Link Aggregation (Wide ports) Full Duplex 1.5 Gb/sec 3.0 Gb/sec 3.0 Gb/sec (at intro.) (6.0 Gb/s planned) 2.0 Gb/sec 4.0 Gb/sec Connectivity 1 m internal cable>6m external cable>15m external cable One device (fan-out devices demonstrated) >128 devices Expanders (16k Phys. max) 127 devices Loop or loop switch SATA onlySAS and SATAFibre Channel only Availability Single port HDDsDual-port HDDs Single-host Point-to-point Multi-initiator Point-to-point Multi-initiator Shared media or point-to-point Device Compatibility SATA onlySAS and SATA devicesFibre Channel only

15. NEC Computers SAS - Confidentiel - Feb. 2008 - SAS Technology 15 “Comparison” OSI / SAS OSITCP/IPSAS ApplicationHTTP, FTP, SNMP…N/A PresentationHTTP, FTP, SNMP…N/A SessionTCPSATA, SSP TransportTCPSMP, STP NetworkIPSAS Address Data LinkMACWWN PhysicalEthernet CableSAS cable