SCSI命令概述(翻译)解读

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SCSI Overview
WRITE (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
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SCSI 命令概述
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SCSI Overview
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
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SCSI Overview
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SCSI Overview
数据块指定的指令
• READ CAPACITY • VERIFY • WRITE AND VERIFY • READ LONG • WRITE LONG • Many more…
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SCSI Overview
Streaming Specific Commands
• • • • • • • • LOAD UNLOAD LOCATE (16) PREVENT ALLOW MEDIUM REMOVAL READ BLOCK LIMITS READ POSITION REWIND SET CAPACITY SPACE (16)
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SCSI Overview
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
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SCSI Overview
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 and that the target can remove it from its local cache
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 accessed again in the near future and that the target can remove it from its local cache
本地单元使典型的512字节（1数据块）
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SCSI Overview
READ (16) Command
• Restricted for MMC-4
– Used for the MMC-4 Version of this command
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SCSI Overview
READ (16) Command
*不同的域定义使用相同的 CDB长度
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SCSI Overview
Command SCSI Commands in SAS
• Write Commands
– WRITE (6) (SSC and SBC)* – WRITE (10) (SBC) – WRITE (12) (SBC) – WRITE (16) (SBC) – WRITE (32) (SBC)
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SCSI Overview
WRITE (16) Command
• Restricted for MMC-4
– Used for the MMC-4 Version of this command
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SCSI Overview
WRITE (16) Command
• Group Number
– Used to collect performance statistics of different groups of commands – Application A’s performance vs. Applications B’s performance
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SCSI Overview
WRITE (16) Command
• Transfer Length
– Specifies the length in contiguous logical units to be transferred in this command – Logical unit is typically 512-bytes (1 Block)
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SCSI Overview
Common SCSI Commands in SAS
• Read Commands
– READ (6) (SSC and SBC)* – READ (10) (SBC) – READ (12) (SBC) – READ (16) (SBC) – READ (32) (SBC)
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SCSI Overview
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
*Different Field Definitions, same CDB Length
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SCSI Overview
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) TEST UNIT READY (SPC) MODE SENSE (SPC) MODE SELECT (SPC) LOG SENSE (SPC) LOG SELECT (SPC) READ ATTRIUBUTE (SPC) REPORT LUNS (SPC)
适用于目标内部缓存并且指示其接近媒介
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SCSI Overview
READ (16) Command
• Logical Block Address (LBA)
逻辑区块地址
– 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
关于写保护检查的多种设定read16commanddisablepageoutbitlogicalblockaddressaccessedagainnearfuturetargetcanremovefromitslocalcacheset1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read16commandforceunitaccessnonvolatiletargetsinternalcachingmedia适用于目标内部缓存并且指示其接近媒介read16commandlogicalblockaddresslbainitiatorwouldliketargetconvertscylindersectorheadaddresscomputersystemuser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read16commandtransferlengthcontiguouslogicalunitslogicalunittypically512bytesblock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read16commandmmc4versioncommandread16commandgroupnumbercollectperformancestatisticsdifferentgroupsperformancevs
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SCSI Overview
WRITE (16) Command
• Logical 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
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
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SCSI Overview
READ (16) Command
• Transfer Length
在此对象中指定在临近逻辑单元上被转移的长度
– Specifies the length in contiguous logical units to be transferred in this command – Logical unit is typically 512-bytes (1 Block)
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SCSI Overview
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
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SCSI Overview
WRITE (16) Command
• OP Code: 8Ah Specifies the command • WD Protect: Various settings regarding the write protection checking
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SCSI Overview
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SCSI Overview
TEST UNIT READY Command
Also: CHECK CONDITION – NOT READY – POWER ON OCCURED
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SCSI Overview
INQUIRY Commaand • EVPD: Enable Vital Product Data
• Group Number
用于收集不同组别命令的执行统计
– Used to collect performance statistics of different groups of commands – Application A’s performance vs. Applications B’s performance
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
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SCSI Overview
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
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
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SCSI Overview
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 Streaming 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)
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SCSI Overview
READ (16) Command
• Control
– – – –
翻译：标准SCSI控制字节
Standard SCSI Control Bytes Defined in SAM-4 Has a consistently defined meaning across all commands\ Found only on fixed-length CDB commands