External Path Protection

Transcription

1 June 26, 2008 T13/e07162r2-External_Path_Protection.fm External Path Protection June 26, 2008 Revision 2 Technical Editor: Curtis E. Stevens Lake Forest Dr. Lake Forest, Ca Curtis.Stevens@wdc.com 1

2 T13/e07162r2-External_Path_Protection.fm June 26, 2008 Document Status Revision History Rev Date Description 0 June 15, ) Initial Revision 0a September 12, ) Restructured SET FEATURES 2) Changed terminology to better match SBC/SPC 3) Aligned features with T10 Protection Information Types 0b September 12, ) Added counters to match associated features 0c September 14, ) Fixed typo s 2) Added editors notes to show equivalency to T10 Protection Information. This information may need to be replicated in an informative annex. 1 October 17, ) Incorporated comments from Kevin Marks 1) Changed all host references to application client 2) Added SBC-3 to references 3) Fixed the polarity of the PIT bit 4) Made other minor changes 2) Incorporates commetns from Bill Martin 2 June 26, ) Added mechanism to allow queued commands to enable/disable the various External Path Protection features. 2

3 June 26, 2008 T13/e07162r2-External_Path_Protection.fm 1 Introduction SCSI Block Devices have a feature called Protection Information which is described in SBC This feature allows the application client to append 8 bytes of protection information to a sector of user data. ATA devices are increasingly being used in traditional SCSI/SAS environements and need a mechanism which allows them to map the Protection Information Model to ATA devices. 2 Changes to ACS 2.1 Changes to clause Changes to Approved ANSI References Replace the references listed with the new references for this proposal. Name Reference Protected Area Run Time Interface Extensions (PARTIES) ANSI INCITS SCSI Primary Commands - 3 (SPC-3) ANSI INCITS ISO/IEC Changes to ANSI References Under Development Replaces the references listed below with the new references for this proposal. Name AT Attachment-8 - Parallel Transport (ATA8-APT) AT Attachment-8 ATA/ATAPI Architecture Model (ATA8-AAM) SCSI Block Commands - 3 (SBC-3) Project Number INCITS 1698D ISO/IEC INCITS 1700D ISO/IEC INCITS 1799D Changes to Other References Replace the references list below with the new references for this proposal. PC Card Standard, February 1995, PCMCIA (68-pin Connector) For the PC Card Standard published by the Personal Computer Memory Card International Association, contact PCMCIA at or CompactFlash Association Specification, Revision 4.0 For the CompactFlash Association Specification published by the CompactFlash Association, contact the CompactFlash Association at 3

4 T13/e07162r2-External_Path_Protection.fm June 26, Changes to clause Changes to Definitions and abbreviations Your Term: Definition Your Term: Definition. 2.3 Changes to clause Overview - Changes to the Feature Set Summary Table Replace the names of the feature sets in the table below with the new feature set names. Feature set General Devices Packet Devices External Path Protection (see TBD) O P Your feature set (see TBD) O O Key: M Mandatory, O Optional, P Prohibited, N Not defined External Path Protection (EPP) feature set Overview The External Path Protection (EPP) feature set allows the application client or the device to add an extra 8 bytes to the user data. This extra 8 bytes is referred to as Protection Information (PI). EPP requires that the media be formatted with sectors that are 8 bytes larger than the expected user data. For example, if the user data is measured in 512 byte units, the media is formatted in 520 byte units. When EPP is implemented on a device which accepts 512 bytes of user data per LBA, IDENTIFY DEVICE data shall reflect the difference in size when the protection information is transferred (see )xxx by indicating that the device has a logical sector size of 260 words in IDENTIFY DEVICE data words and IDENTIFY DEVICE data word 106 bit 12 shall be set to 1. Compatibility with application clients the do not manipulate the protection information may be achieved by disabling the transfer of proteciton information. In this mode, the IDENTIFY DEVICE data shall reflect the size when the protection information is not transferred (see )xxx by indicating that the device has a logical sector size of 256 words in IDENTIFY DEVICE data words and IDENTIFY DEVICE data word 106 bit 12 shall be set to 0. The External Path Protection log (see x.x.x) is mandatory for devices implementing EPP. Table 1xxx describes one logical block of data transferred in a device which implements External Path Protection: Table 1 Protection Format Offset User Data n-1 n (LSB) Logical Block Guard (LBG) (see ) n+1 (MSB) n+2 Logical Block Application Tag (LBAT) (see ) n+3 n+4 (LSB) Logical Block Reference Tag (LBRT) (see ) n+7 (MSB) The device may check these fields during read and write operations to confirm that the User Data is correct based on the current checking modes. The External Path Protection log provides the application client with flexibility in the checking and setting of LBG, LBAT, and LBRT: a) Enable/Disable LBG checking b) Enable/Disable LBRT checking 4

5 June 26, 2008 T13/e07162r2-External_Path_Protection.fm c) Enable/Disable Protection Information Transfer d) Controls for setting the Protection Information fields during writes when Protection Information Transfer is disabled. e) Escape Type (see )xxx Devices which implement EPP shall be formatted at the time of manufacture to the size of the user data plus eight bytes. For example, if the Logical Sector Size for the user data is 512 bytes, the device reports a Logical Sector Size of 520 bytes when Protection Information Transfer (see )xxx is enabled. The protection information is not initialized until the proper EPP Control settings are enabled and the application client writes the Protection Information for each sector. For example, if the application client wishes to enable LBG checking and LBRT checking, the following procedure may be followed: 1) Disable Protection Information Transer 2) set EPP Control to Generate LBG and LBRT 3) Issue SCT Write Same command with Start=0000_0000_0000_0000h and Count=0000_0000_0000_0000h This will cause the device to write valid Protection Information in all the sectors Logical Block Guard (LBG) EPP Control is used to inform the device how to process the LBG field. The device shall process the LBG field in one of the following ways: a) a 16-bit field which contains a CRC calculated based on the User Data; or b) as Application Client specific information. If the LBG field is Application Client specific information, then the device shall store the information on the media, and disable erorr checking based on this information. If the LBG field contains a CRC, then see SBC-3 Logical Block Guard for a description of the polynomial used to calculate the CRC Logical Block Application Tag (LBAT) LBAT is a 16-bit field which shall be stored on the media with the user data. This value shall only be checked by the device to determine if Escape (see ) is present Logical Block Reference Tag (LBRT) EPP Control is used to inform the device how to process the LBRT field. The device shall process the LBRT field in one of the following ways: a) a 32-bit field which contains LBA (31:0) of the sector being processed by the device; or b) as Application Client specific information. If the LBRT field is Application Client specific information, then the device shall store the information on the media, and disable erorr checking based on this information. If the LBRT field contains LBA (31:0) of the sector being processed, then EPP Control may be used to set checking option for LBRT Escape Type EPP Control Escape Type sets the conditions which cause the device to ignore the protection information. See for more information on Escape type. EPP Control Escape Check (see ) may be used to prevent the device from checking for an Escape. 5

6 T13/e07162r2-External_Path_Protection.fm June 26, Changes to clause Changes to DCO Set If the proposal adds a feature set or command, there may be be an addition to the Device Configuration Set data structure and the Device Configuration Identify data structure to allow the capability to be removed from the device. Fill in the description in the table and place a description of each bit or word underneath the table. This one table will indicate the changes for both. Word TBD Command set/feature set supported TBD1 External Path Protection Content Word TBD bit TBD1 if set to one indicates that the device is allowed to report support for External Path Protection [Add DCO Identify separatly.] Changes to IDENTIFY DEVICE data If the proposal adds a feature set or command, there should be an addition to the IDENTIFY DEVICE data to indicate both supported and enabled descriptions. Fill in the description in the table and place a description of each bit or word underneath the table. Word O M S P F V Description TBD A O B External Path Protection Bit Descritpion F 15 External Path Protection feature set supported V 14 LBG Checking enabled V 13 LBRT Checking Enabled V 12 Escape Generation Enabled V 11 Protection Information Transfer Enabled F 10 Enable/Disable Error On Escape Supported V 9 Escape Check Enabled F 8:0 Reserved Key: O/M Mandatory/optional requirement. M Support of the word is mandatory. O Support of the word is optional. F/V Fixed/variable content F The content of the field is fixed and does not change. The DCO command may change the value of a fixed field. For removable media devices, these values may change when media is removed or changed. V The contents of the field is variable and may change depending on the state of the device or the commands executed by the device. X The content of the field may be fixed or variable S/P Content applies to Serial or Parallel transport S Serial Transport P Parallel Transport B Both Serial and Parallel Transports N Belongs to a transport other than Serial or Parallel TBD A External Path Protection If bit 15 is set to one then the External Path Protection feature set is supported If bit 14 is set to one, then LBG Checking is enabled. If bits 15 is cleared to zero, then bit 14 shall be reserved. If bit 13 is set to one, then LBRT Checking is enabled. If bit 15 is cleared to zero, then bit 13 shall be reserved. 6

7 June 26, 2008 T13/e07162r2-External_Path_Protection.fm If bit 12 is set to one, then Escape Generation is enabled. If bit 15 is cleared to zero, then bit 12 shall be reserved. If bit 11 is set to one, then Protection Information Transfer is enabled. If bit 15 is cleared to zero, then bit 11 shall be reserved. If bit 10 is set to one, then the EPP Control for Enable/Disable Escape Check is supported. If bit 15 is cleared to zero, then bit 10 shall be reserved. If bit 9 is set to one, then Escape Check is enabled. If bits 15 or 10 are cleared to zero, then bit 9 shall be reserved. Bits 8:0 are reserved. 7

8 T13/e07162r2-External_Path_Protection.fm June 26, New External Path Protection (EPP) log EPP Control Overview The EPP log is mandatory for devices implementing the EPP feature set. When the application client writes this log, the settings shall be non-volatile. Table 2 describes the EPP log. Table 2: External Path Protection log Byte Type Description 0 Word Non-queued Capabilities Bit Description 15:8 Reserved 7 1=LBG Checking enabled 6 1=LBRT Checking enabled 5 1=Escape Generation enabled 4 1=Protection Information Transfer enabled 3 1=Escape Check enabled 2:0 Reserved 2 Word Queued LBG Checking enabled 15:8 Low Tag 7:0 High Tag 4 Word Queued LBRT Checking enabled 15:8 Low Tag 7:0 High Tag 6 Word Queued Escape Generation enabled 15:8 Low Tag 7:0 High Tag 8 Word Protection Information Transfer enabled 15:8 Low Tag 7:0 High Tag 10 Word Queued Escape Check enabled 15:8 Low Tag 7:0 High Tag Reserved 8

9 June 26, 2008 T13/e07162r2-External_Path_Protection.fm Editor s Note 1: Could add an entry to set the non-escape value LBG Checking If LBG Checking is enabled, the device shall check the LBG prior to transferring User Data. If the LBG is not correct, then the device shall fail the associated read commands with an Uncorrectable error and shall fail the associated write commands with an ID Not Found. If EC is enabled, then the device shall not generate an error if an Escape is encountered (see for more information on Escape). Editor s Note 2: Enabled is equivalent to setting RDPROTECT to 000b, 001b, 101b, 100b or WRPROTECT to 001b, 100b, or 101b. Disabled is equivalent to setting RDPROTECT to 010b, 011b or WRPROTECT to 010b and 011b. Editor s Note 3: This differs slightly from T-10 Protection which specifies that on writes when WRPROTECT=000b then no checking is performed. The protection information is generated by the device and may have the possibility of becoming corrupt before the last check point. Therefore, the device should be able to report an error when WRPROTECT=000b LBRT Checking If LBRT Checking is enabled, the device shall check the LBRT prior to transferring User Data. If the LBRT is not equal to bits 31:0 of the requested LBA, then the device shall fail the associated read commands with an Uncorrectable error and the associated write commands with an ID Not Found. If EC is enabled, then the device shall not generate an error if an Escape is encountered (see for more information on Escape). Editor s Note 4: Enabled is equivalent to setting RDPROTECT to 000b, 001b, 010b, 101b, or WRPROTECT to 001b, 010b, 101b. Disabled is equivalent to setting RDPROTECT to 011b, 100b or WRPROTECT to 011b and 100b. Editor s Note 5: This differs slightly from T-10 Protection which specifies that on writes when WRPROTECT=000b then no checking is performed. The protection information is generated by the device and may have the possibility of becoming corrupt before the last check point. Therefore, the device should be able to report an error when WRPROTECT=000b Escape Generation (EG) If PIT is enabled then EG shall be ignored. If PIT is disabled and EG is disabled then the device shall calculate and insert the CRC for the USER data in the LBG field and shall place bits 31:0 of the LBA of the sector currently in transit in the LBRT field when the device processes write commands. If PIT is disabled and EG is Enabled then the device shall place an Escape in the Protection Information fields (See for more information on Escape) Editor s Note 6: This is roughly equivalent to the ATO bit setting in T10 Protection Information. 9

10 T13/e07162r2-External_Path_Protection.fm June 26, Escape Type If EC (see ) is enable and ET is set to zero then a) If PIT is disabled and EG is enabled then the device shall set LBAT to FFFFh for each sector received from the application client. b) If PIT is enabled then if the device receives a sector from the Application Client with LBAT set to FFFFh then the device shall not check LBG or LBRT for errors at any point during the write process. c) If the device sends a sector to the Application Client with LBAT set to FFFFh then the device shal not check LBG or LBRT for errors at any point during the read process. If EC (see ) is disabled and ET is set to one then a) If PIT is disabled and EG is enabled then the device shall set LBAT to FFFFh and LBRT set to FFFF_FFFFh for each sector received from the application client. b) If PIT is enabled then if the device receives a sector from the application client with LBAT set to FFFFh and LBRT set to FFFF_FFFFh then device shall not check LBG or LBRT for errors at any point during the write process. c) If the device sends a sector to the Application Client with LBAT to FFFFh and LBRT to FFFF_FFFFh then the device shal not check LBG or LBRT for errors at any point during the read process. Editor s Note 7: This is roughly equivalent to setting type 1/2 or type 3 protection Protection Information Transfer (PIT) When PIT is disabled, the device shall add 8 bytes of Protection Information to the user data as the user data is received from the application client and strip off the 8 bytes of Protection Information before transferring data to the application client. This does not change the format of the data on the media. In this mode, the application client has configured the device to generate the Protection Information and that the application client should not be sending Protection Information to the device with the user data. When PIT is disabled, if the application client sends Protection Information to the device, the protection information shall be interpreted as user data. If PIT is disabled, then the device shall indicate a logical sector size in IDENTIFY DEVICE words that does not include the 8 bytes of Protection Information. For example, if PIT is enabled, and IDENTIFY DEVICE data words indicate a size of 260 words; then when PIT is disabled, IDENTIFY DEVICE data words change to 256. If PIT is enabled, 8 bytes of Protection Information shall be transferred with each sector of user data for read and write commands. Editor s Note 8: PIT=0 is equivalent to setting RDPROTECT or WRPROTECT to 000b. PIT=1 is equivalent to setting RDPROTECT or WRPROTECT >000b Escape Check (EC) If EC is disabled then the device shall not check the Protection Information for an Escape. If EC is enabled then the device shall check the Protection Information for an Escape as described in Editor s Note 9: This capability is not duplicated in SBC-3 or SPC Volatile If Volatile is cleared to zero then the device shall preserve the EPP Control value across all resets. If the Volatile bit is set to one then 10

11 June 26, 2008 T13/e07162r2-External_Path_Protection.fm a) if the device processes a hardware or software reset then the device shall preserve the EPP Control value b) if the device processes a power-on reset then it shall use the last EPP Control value it received with the Volatile bit cleared to zero. Editor s Note 10: This is needed because the checking modes are not specified by command and there is no type information due to the lack of a FORMAT UNIT command New Counters Editor s Note 11: SCSI does not define standard counters for these errors. It is WD s opinion that making these counters available can help with tech support issues as well as helping the end user (near line storage developers) debug system issues. The following new counters report statistics associated with External Path Protection: Table A.1 EPP Statistics Offset Type Content 0-7 QWord Structure Version 63:16 Reserved 15:0 0001h 8-15 Qword Lifetime Total EPP errors detected 31:0 Total number of liftime errors detected by the EPP feature set 8-15 Qword Lifetime LBG failures receiving write data 31:0 Number of times that the CRC was invalid when LBG was received from the Application Client. Editor s Note 12: data was invalid when received from the application client Qword Lifetime LBRT failures receiving write data 31:0 Number of times that LBA (31:0) was invalid when LBRT was received from the Application Client. Editor s Note 13: data was invalid when received from the application client 11

12 T13/e07162r2-External_Path_Protection.fm June 26, 2008 Table A.1 EPP Statistics Offset Type Content Qword Lifetime LBG write failures after data received 31:0 Number of times that the CRC became invalid after it was verified as good when the data was received from the Application Client. Editor s Note 14: Data became corrupt in the device Qword Lifetime LBRT write failures after data received 31:0 Number of times that LBA (31:0) became invalid after it was verified as good when the data was received from the Application Client. Editor s Note 15: Data became corrupt in the device Qword Lifetime LBG failures during read from media 31:0 Number of times that the CRC was found to be invalid while reading data from the media. Editor s Note 16: This could be caused by many things. Checking was disabled during the write and bad data was sent during the write. Checking was subsequently enabled and the error is being detected. Error could also be generated due to unformatted LBG. Checking could have been disabled, good data provided that went bad before it was written to the media. 12

13 June 26, 2008 T13/e07162r2-External_Path_Protection.fm Table A.1 EPP Statistics Offset Type Content Qword Lifetime LBRT failures during read from media 31:0 Number of times that LBA (31:0) was found to be invalid while reading data from the media. Editor s Note 17: This could be caused by many things. Checking was disabled during the write and bad data was sent during the write. Checking was subsequently enabled and the error is being detected. Error could also be generated due to unformatted LBRT. Checking could have been disabled, good data provided that went bad before it was written to the media Qword Lifetime LBG failures after read from media 31:0 Number of times that the CRC was found to be invalid prior to sending data to the Application Client. Editor s Note 18: Data became corrupt in the device Qword Lifetime LBRT failures after read from media 31:0 Number of times that LBA (31:0) was found to be invalid prior to sending data to the Application Client. Editor s Note 19: Data became corrupt in the device 13

14 T13/e07162r2-External_Path_Protection.fm June 26, 2008 Table A.1 EPP Statistics Offset Type Content Qword Lifetime number of write commands processed with LBG checking disabled 31:0 Number of write commands received when LBG checking is disabled. Editor s Note 20: This could lead to LBG read from the media failure detections. If this number is zero, then LBG failures are probably the result of the data going bad in the device Qword Lifetime number of read or write commands processed with LBRT checking disabled 31:0 Number of write commands received when LBRT checking is disabled. Editor s Note 21: This could lead to LBRT read from the media failure detections. If this number is zero, then LBRT failures are probably the result of the data going bad in the device Byte Reserved 14