Protocol Overview The SCSI Protocol 2005 Cisco

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M01L01_SCSI_Overview_0424_dsl.ppt

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Outline • SCSI Protocol Overview • SCSI Architecture Model • SCSI Parallel Technology • SCSI Operation • SCSI Commands and Status • SCSI Messages • Summary © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -2

SCSI Protocol Overview • SCSI performs passing commands, status, and block data between initiators and targets • SCSI is a hierarchy of functions to assemble raw data blocks into application readable files Initiator Target Requests Application Client LUNs Responses Device Server Tasks Delivery Subsystem [ parallel or FCP or IP ] © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -4

Multidrop Topology and Addressing Multidrop Topology SCSI Initiator (I/O Adapter) Terminator Data/Address Bus Control Signals Interface ID ID ID 7 6 5 Interface … ID 0 Priority © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -6

Multi-Drop Topology and Addressing (cont. ) Addressing Data/Address Bus SCSI Initiator (I/O Adapter) Control Signals Interface LUN 0 LUN 1 LUN 2 LUN 3 Address = BUS : Target ID : LUN © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -7

SCSI Architecture Model (cont. ) SPC *SCSI-3 Class Drivers SCSI Parallel Port Driver SCSI-3 FCP Port Driver i. SCSI IP Port Driver SAS Port Driver SCSI Serial Bus Protocol (SBP-2) Port Driver SCSI Parallel Port Fibre Channel Port Ethernet Port SAS Serial Port IEEE-1394 (Firewire) Port Serial Attached SCSI Interface FC SCSI Card FC Card Firewire Interface NIC *SCSI-3 – Separation of physical interface, transport protocols, and SCSI Command Set © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -9

SCSI Operation SCSI includes three phases of operation • Command – send the required command parameters via a Command Descriptor Block (CDB) • Data – Transfer data in accordance with the command • Status – Receive confirmation of command execution Initiator © 2005 Cisco Systems, Inc. All rights reserved. Target M 01 L 01 vx. x—L 01 -11

SCSI Operation (cont. ) SCSI Bus Arbitration • Arbitrate for the SCSI Bus and take control SCSI Device Selection Connection , Arbitrate a nd select • Address the Target by it’s SCSI ID and select it SCSI Command SCSI Read CMD (28 h) Command Phase • Send required command parameters via a Command Descriptor Block (CDB) SCSI Data (optional) s Data In Pha e DATA • Transfer Data in accordance with the command SCSI Status or Response • Receive confirmation of command execution se Status Pha RSP SCSI Message • Send ‘Command Complete’ message • Release the Bus © 2005 Cisco Systems, Inc. All rights reserved. Disconnect M 01 L 01 vx. x—L 01 -12

SCSI Commands and Status SCSI Command Descriptor Block (CDB) Byte 0 1 2 3 4 5 6 7 8 9 7 6 5 Group Code 4 3 2 1 0 Command Code First Byte – Operation Code Reserved Service Action Logical Block Address MSB Logical Block Address Reserved Transfer Length Control Transfer Data starting at this LBA LSB Number of SCSI Blocks to be transferred LSB Last Byte – Control Byte • A Command is executed by sending a CDB to a Target. © 2005 Cisco Systems, Inc. All rights reserved. M 01 L 01 vx. x—L 01 -14

SCSI Commands and Status (cont. ) Standard SCSI Commands across all devices Op Code Command Name 00 h Test Unit Ready 03 H Request Sense 12 h Inquiry 15 h Mode Select 18 h Copy 1 Ah Mode Sense hex Status 1 Ch Receive Diagnostic Results 00 Good 1 Dh Send Diagnostic 02 Check Condition 39 h Compare 04 Condition Met 3 Ah Copy and Verify 08 Busy 3 Bh Write Buffer 10 Intermediate 3 Ch Read Buffer 14 Intermediate-Condition Met 4 Ch Log Select 18 Reservation Conflict 4 Dh Log Sense 28 Task Set Full 55 h Mode Select 30 ACA Active 5 Ah Mode Sense . . © 2005 Cisco Systems, Inc. All rights reserved. Once a SCSI Command is sent to a Target, Initiator expects a status. M 01 L 01 vx. x—L 01 -16