SCSI命令概述(翻译).ppt

1、UNH 互操作性实验室,SCSI 命令概述,物理,物理层,数据链路层,数据传输层,应用层,陈述主题,命令摘要 命令选择释义 附加意义上的代码及资格,CDB,命令数据程序块 命令由CDBs定义 每个对象都有他自己的 CDB CDBs 由多种SCSI标准定义 拥有固定和变化的长度变量 In SAS: 囊括在一个指令框架中,SCSI Command Sets,SPC-4 SCSI Primary Commands Version 4 命令对于所有的方法类型普遍适用 SBC-3 SCSI Block Command Version 3 命令针对特定的块设备 (硬盘) SSC-2 SCSI Stream

2、ing Commands Version 2 命令针对特定的流设备(磁盘驱动) MMC-4 SCSI Multi Media Commands Version 4 命令针对特定的多媒体设备(CD/DVD),Common SCSI Commands in SAS,Read Commands READ (6) (SSC and SBC)* READ (10) (SBC) READ (12) (SBC) READ (16) (SBC) READ (32) (SBC) *不同的域定义使用相同的 CDB长度,Command SCSI Commands in SAS,Write Commands WRIT

3、E (6) (SSC and SBC)* WRITE (10) (SBC) WRITE (12) (SBC) WRITE (16) (SBC) WRITE (32) (SBC) *Different Field Definitions, same CDB Length,诊断与初始化指令,读缓冲(SPC) 写缓冲 (SPC) 询问(SPC) 测试单元就绪(SPC) 模式识别(SPC) 模式选择(SPC) 日志识别(SPC) 日志选择(SPC) 读取归类(SPC) REPORT LUNS (SPC),READ BUFFER (SPC) WRITE BUFFER (SPC) INQUIRY (SPC

4、) TEST UNIT READY (SPC) MODE SENSE (SPC) MODE SELECT (SPC) LOG SENSE (SPC) LOG SELECT (SPC) READ ATTRIUBUTE (SPC) REPORT LUNS (SPC),数据块指定的指令,READ CAPACITY VERIFY WRITE AND VERIFY READ LONG WRITE LONG Many more,Streaming Specific Commands,LOAD UNLOAD LOCATE (16) PREVENT ALLOW MEDIUM REMOVAL READ BLOC

5、K LIMITS READ POSITION REWIND SET CAPACITY SPACE (16),READ (16) Command,OP 代码: 88h Specifies the command 读保护: 关于写保护检查的多种设定,READ (16) Command,DPO Disable Page Out Bit 用于最优化登录目标设备的缓存 Set to 1 tells the target that data at this Logical Block Address is not likely to be accessed again in the near future

6、 and that the target can remove it from its local cache,Set to 1告诉目标在这个逻辑区块地址中的数据在不久的将来无法再次接近并且目标可在将它从它的本地缓存中移除,READ (16) Command,FUA and FUA_NV Force Unit Access (Non-Volatile) Used to override the targets internal caching and force it to access the media,适用于目标内部缓存并且指示其接近媒介,READ (16) Command,Logica

7、l Block Address (LBA) The address on the medium that the initiator would like to read Internally, the target converts the LBA to a (Cylinder, Sector, Head) address Transparent to the computer system and user,逻辑区块地址,在内部，对象将LBA转化成一个地址，此地址对计算机系统和用户而言显而易见,READ (16) Command,Transfer Length Specifies the

8、length in contiguous logical units to be transferred in this command Logical unit is typically 512-bytes (1 Block),本地单元使典型的512字节（1数据块）,在此对象中指定在临近逻辑单元上被转移的长度,READ (16) Command,Restricted for MMC-4 Used for the MMC-4 Version of this command,READ (16) Command,Group Number Used to collect performance st

9、atistics of different groups of commands Application As performance vs. Applications Bs performance,用于收集不同组别命令的执行统计,READ (16) Command,Control Standard SCSI Control Bytes Defined in SAM-4 Has a consistently defined meaning across all commands Found only on fixed-length CDB commands,翻译：标准SCSI控制字节,WRIT

10、E (16) Command,OP Code: 8Ah Specifies the command WD Protect: Various settings regarding the write protection checking,WRITE (16) Command,DPO Disable Page Out Bit Used to optimize caching onboard the target device Set to 1 tells the target that data at this Logical Block Address is not likely to be

11、accessed again in the near future and that the target can remove it from its local cache,WRITE (16) Command,FUA and FUA_NV Force Unit Access (Non-Volatile) Used to override the targets internal caching and force it to access the media,WRITE (16) Command,Logical Block Address (LBA) The address on the

12、 medium that the initiator would like to read Internally, the target converts the LBA to a (Cylinder, Sector, Head) address Transparent to the computer system and user,WRITE (16) Command,Transfer Length Specifies the length in contiguous logical units to be transferred in this command Logical unit i

13、s typically 512-bytes (1 Block),WRITE (16) Command,Restricted for MMC-4 Used for the MMC-4 Version of this command,WRITE (16) Command,Group Number Used to collect performance statistics of different groups of commands Application As performance vs. Applications Bs performance,WRITE (16) Command,Cont

14、rol Standard SCSI Control Bytes Defined in SAM-4 Has a consistently defined meaning across all commands Found only on fixed-length CDB commands,TEST UNIT READY Command,OP Code: 00h Specifies the command Control Bits are typically zero Defined in SAM-4 Result: 6 Byte CDB consisting of entirely 0s,TES

15、T UNIT READY Command,Also: CHECK CONDITION NOT READY POWER ON OCCURED,INQUIRY Command,OP Code: 12h Specifies the Command EVPD: Enable Vital Product Data Set to zero, the device returns standard inquiry data Set to one, enables the page code field,设置为0，设备返回普通的询问信息,设置为1，启用页面代码字段,INQUIRY Command,Page C

16、ode: Specifies the page code to return. Pages are defined in SAM-4, SPC-4, and technology specific standards Allocation Length specifies the length of inquiry data the initiator is prepared to accept in bytes,定位长度决定了发起者准备接收的询问信息的长度,REPORT LUNS Command,OP Code: A0h Specifies the command Select Report

17、:,REPORT LUNS Command,Allocation Length should be at least 16 bytes If the allocation length is insufficient to report all the LUNs on the device, the device shall report only what it is able to report,翻译：定位长度至少要有16字节,翻译：如果定位长度不足以报告设备上所有的逻辑单元，硬盘应该只报告它可以报告的单元,Additional Sense Codes,Values returned in a Response Frame (SAS) in the event that a command could not be completed So many possible problems that a qualifier is used to expand the poo