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

NEC Computers SAS - Confidentiel - Feb 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.

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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)

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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

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

NEC Computers SAS - Confidentiel - Feb 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 _ h represents invalid address Each SAS device has a different WWN

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

NEC Computers SAS - Confidentiel - Feb 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

NEC Computers SAS - Confidentiel - Feb 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