ddptctl - Man Page

ddptctl [--abort] [--all_toks] [--block] [--del_tkn] [--flexible] [--help] [--immed] [--info] [--list_id=LID] [--oir=OIR] [--poll] [--pt=GL] [--readonly] [--prefer_rcs] [--receive] [--rtf=RTF] [--rtype=RTYPE] [--size] [--timeout=ITO[,CMD]] [--verbose] [--version] [--wut=SL] [DEVICE]

This utility is a helper/auxiliary for the ddpt utility which copies data between or within SCSI devices (logical units). While ddpt's command line syntax is modelled on that of the POSIX dd command, this utility has a more standard Unix command line syntax with both short and long variants of each option.

The T10 committee defines a family of SCSI commands for offloaded copy. The central (but not the only) command is EXTENDED COPY often shortened to XCOPY or xcopy. There are now two generations of xcopy, the older one is given the suffix "LID1" and the newer one: "LID4". There is a subset of XCOPY(LID4) that supports disk to disk copies and is based on the SBC-3 commands: POPULATE TOKEN (PT) and WRITE USING TOKEN (WUT). ODX is a market name that has become associated with this subset. This utility can issue PT, WUT and related commands, read the Third Party Copy VPD page and perform several other housekeeping tasks.

The xcopy family of commands are described in the SPC-4,5 and SBC-3,4 documents found at https://www.t10.org .

Apart from PT and WUT, other command abbreviations used below are RRTI for the RECEIVE ROD TOKEN INFORMATION command and RCS for the RECEIVE COPY STATUS(LID4) command.

Arguments to long options are mandatory for short options as well.

-A,  --abort

this option will issue the COPY OPERATION ABORT command with the LID given in the --list_id=LID option. If the --list_id=LID option is not given then its default LID (257) is used. If there is an xcopy operation ongoing on this I-T nexus (i.e. issued by this machine to any LU sharing the same target) using that LID then the copy is aborted. Note there is a sense key (COPY ABORTED) indicating some but not all data has been copied due to this action.

-a,  --all_toks

send the REPORT ALL ROD TOKENS SCSI command to DEVICE and decode the response. An ODX implementation is not required to support this command.

-B,  --block

treat DEVICE as a block device when checking its --size. The default action of this utility is to treat DEVICE as a SCSI pass-through device.

-D,  --del_tkn

set the DEL_TKN bit in a WUT command (default: clear the DEL_TKN bit). Since an ODX copy manager deletes the ROD Token when its inactivity time-out is reached, this option is typically not needed. It may be useful for long-lived ROD Tokens that are no longer needed.
To delete an unused ROD Token a degenerate scatter list seems to be acceptable (e.g. '--wut=0,0 --del_tkn').

-f,  --flexible

this option currently only effects the parsing of sgl_s in files that are in hexadecimal plus they have a leading line with 'HEX' in them. Without this option any such line must be invoked with 'H@' before the filename; in other words the 'H' in the invocation needs to match the HEX in the file. With this option a sgl in a file can be invoked with '@' and if a line with HEX is parsed before any LBA,NUM pairs then it switches to hexadecimal mode; so all the parsed LBA,NUM pairs are assumed to be in hexadecimal.

-h,  --help

outputs the usage message summarizing command line options then exits.

-I,  --immed

set the IMMED bit in the PT or WUT command. When given the PT and WUT commands return promptly before the data transfer is complete; then this utility exits. The user should then invoke the utility again with the --poll option and the same LID and DEVICE to await completion and receive the final transfer count. The default action of PT and WUT (i.e.  without this option) is to wait for completion (i.e. all data transferred or an error occurs) before exiting this utility.

-i,  --info

when the DEVICE argument is given then check its Third Party Copy VPD page and print out anything found. Also check if the 3PC bit is set in the standard INQUIRY response.
If the DEVICE argument is not given and the --rtf=RTF option is given then decode part of the ROD Token held in the --RTF file. SPC-4 defines some parts of a ROD Token that can be decoded but does not require the copy manager to set these fields; so many fields may appear as zeros. A --RTF file that has been generated by the ddpt utility may contain multiple ROD Tokens, each optionally followed by an 8 byte "number of bytes represented" integer. They are all decoded, based on --RTF file length which should either be a multiple of 512 or 520 bytes.

-l,  --list_id=LID

LID is a list identifier which is used to associate an originating xcopy command (e.g. PT or WUT) with a follow-up command that retrieves associated information or aborts the operation. T10 requires each active LID to be unique on a given I-T nexus. An I-T nexus is the current machine (more precisely a HBA if a machine has two or more) and a specific target which will contain one or more logical units (LUs) of which DEVICE is one. If the DEVICE's copy manager feels that rather complex condition has not been met then an error is generated with sense data that decodes to "operation in progress". Rather than try to work out who is doing what elsewhere, try another LID value.
The default value for LID is 257.

-O,  --oir=OIR

OIR is the Offset In ROD, a field in the WUT command. It may be be used together with the --wut=SL option. Its default value is 0 and its units are the logical block size of DEVICE.

-p,  --poll

send RRTI (or RCS) command to the DEVICE using the LID (i.e. from the --list_id=LID option). If a copy status is received indicating the operation is ongoing, then this SCSI command is sent periodically (as suggested by the previous RRTI (or RCS) command or every 500 milliseconds) until some other copy status is detected. If the --list_id=LID option is not given then a LID of 257 is assumed.
If the originating xcopy command was POPULATE TOKEN and the RRTI command indicates that it has completed successfully then the associated ROD Token (returned in the RRTI response) is written to the RTF file. If the --rtf=RTF option is not given then the ROD token is written to a file called ddptctl_rod_tok.bin in the current directory.

-q,  --prefer_rcs

prefers using the RECEIVE COPY STATUS (RCS) command over the RRTI command which is the default. This only should be done following a WUT command since after a PT command, the RRTI command is needed to fetch the ROD tokane.

-P,  --pt=GL

send a POPULATE TOKEN (PT) command with the given gather list. The format of GL is given in the Notes section. If used without the --immed option then this utility, after the PT command finishes successfully, will call the RRTI command. When the RRTI command finishes, potentially with a new ROD Token, this utility will exit. Prior to that exit, if a new ROD Token is available and the --rtf=RTF option is given then that ROD Token is written to the RTF file. If the --rtf=RTF option is not given then the ROD token is written to a file called ddptctl_rod_tok.bin in the current directory.
If the --immed option is given this utility will exit after the PT command finishes. To complete the operation this utility should be invoked again with the --poll option and the same DEVICE.

-y,  --readonly

open the DEVICE read-only (e.g. in Unix with the O_RDONLY flag). The default is to open it read-write.

-R,  --receive

send the RRTI (or RCS) SCSI command to the DEVICE using the LID (i.e. from the --list_id=LID option). If the --list_id=LID option is not given then a LID of 257 is assumed.
If the originating xcopy command was POPULATE TOKEN and the RRTI command indicates that it has completed successfully then the associated ROD Token (returned in the RRTI response) is written to the RTF file. If the --rtf=RTF option is not given then the ROD token is written to a file called ddptctl_rod_tok.bin in the current directory.

-r,  --rtf=RTF

when RTF is a file containing an ODX ROD Token or the name of a file the ROD Token is to be written to. A ROD Token used by ODX is 512 bytes long. If the RTF file was produced by the ddpt utility then it might contain multiple ROD Tokens, each optionally followed by an 8 byte integer containing the "number of bytes represented" by the preceding ROD Token.
If an RTF file with multiple ROD Tokens is given to this utility with --wut=SL then only the first ROD Token is used. If an RTF file is being decoded (i.e. no DEVICE argument given) then all ROD Tokens are decoded.

-t,  --rtype=RTYPE

where RTYPE is the ROD Type, a field in the PT command (apart from "zero"). The default value (0) indicates that the copy manager (in the DEVICE) decides. RTYPE can be a decimal number, a hex number (prefixed by 0x or with a "h" appended) or one of "pit-def", "pit-vuln", "pit-pers", "pit-cow", "pit-any" or "zero". The final truncated word can be spelt out (e.g. "pit-vulnerable"). The "pit-" lead-in stands for "point in time" copy.
The "zero" is a special case and is not given to a PT command. Instead it causes a special Block Device Zero Token to be created that can be used with the --wut=SL option to write blocks of zeros to the given DEVICE.

-s,  --size

prints the number of blocks and the size of each block for the given DEVICE. Protection information is printed if available. By default uses the pass-through interface and the READ CAPACITY command to obtain this information. If the --block option is given then the block layer in the OS is query for size information (and protection information is not reported).

-T,  --timeout=ITO[,CMD]

where ITO is the inactivity timeout (units: seconds) given to the PT command. The default is 0 in which case the copy manager uses its own default which is shown in the Third party Copy VPD page.
CMD is the SCSI command timeout (units: seconds) applied to SCSI commands issued by this utility; default is 0 which is translated to 600 seconds for originating xcopy commands (e.g. PT and WUT) and 60 seconds for other commands. Best not to trigger command timeouts.

-v,  --verbose

increase the level of verbosity, (i.e. debug output).

-V,  --version

print the version string and then exit.

-w,  --wut=SL

send a WRITE USING TOKEN (WUT) command with the given scatter list. The format of SL is given in the Notes section. This option requires the --rtf=RTF option to supply the ROD Token. If used without the --immed option then after the WUT command finishes successfully this utility will call the RRTI command. When the RRTI command finishes this utility will exit.
If the --immed option is given this utility will exit after the WUT command finishes. To complete the operation this utility should be invoked again with the --poll option and the same DEVICE.

The scatter gather list given to the --pt=GL and --wut=SL options in the simplest case contains a pair a numbers, separated by a comma. The first number is the starting LBA and the second number is the number of blocks (no bigger than 32 bits) to read to or write from that starting LBA. Another pair of numbers can appear after that forming the second element of a scatter gather list. Starting LBAs can be in any order but T10 prohibits any logical block appearing more than once in a scatter gather list.

Scatter gather lists can be placed in a file or read from stdin. A file name referring to a file containing a scatter gather list must follow the "@" character (e.g. --pt=@my_sgl.txt"). Reading a list from stdin is indicated by "@-" or "-" (e.g. "--pt=-"). Scatter gather lists in a file have a looser format and can take spaces and tabs as well as a comma as separators. Anything from and including a "#" on a line is ignored.

Both the PT and WUT commands are issued "as is" without checking the Third Party Copy VPD page. The copy manager may well reject these commands (with exit status 51: invalid field in parameter list) if the maximum range descriptors field or the maximum token transfer size field are exceeded.

There is a web page discussing ddptctl and ddpt, XCOPY and ODX at https://sg.danny.cz/sg/ddpt_xcopy_odx.html

The exit status of ddptctl is 0 when it is successful. Otherwise the exit status for this utility is the same as that for ddpt. See the EXIT STATUS section in the ddpt man page.

First issue a PT command without the --immed option so RRTI is called to complete the operation:

 # ddptctl --pt=0x0,10k,20k,5k --rtf=aa.rt /dev/sdb
 PT completes with a transfer count of 15360 [0x3c00]

The transfer count (10k + 5k == 15360) indicates the operation was successful and the ROD Token is in the aa.rt file. Now use that ROD Token to write to the same locations on /dev/sdc:

 # ddptctl --rtf=aa.rt --wut=0x0,10k,20k,5k /dev/sdc
 WUT completes with a transfer count of 15360 [0x3c00]

So the copy was successful. Now taking a closer look at the ROD token:

 # ddptctl --info --rtf=aa.rt
 Decoding information from ROD Token:
   ROD type: point in time copy - default [0x800000]
   Copy manager ROD Token identifier: 0x520000710000000c
   Creator Logical Unit descriptor:
     Peripheral Device type: 0x0
     Relative initiator port identifier: 0x0
     designator_type: NAA,  code_set: Binary
     associated with the addressed logical unit
       0x60002ac0000000000000000c00009502
   Number of bytes represented: 0 [0x0]
   Device type specific data (for disk) has block size of 0; unlikely so skip
   Target device descriptor: unexpected designator type [0x0]

T10 does not require implementations to supply much of the above (only the ROD type and the token length) so expect to see some empty fields.

To see information about /dev/sdb relevant to ODX, try:

 # ddptctl --info /dev/sdb
   /dev/sdb [readcap]: num_blks=209715200 [0xc800000], blk_size=512, 107 GB
 3PC (third party copy) bit set in standard INQUIRY response
  Third Party Copy VPD page:
  Block Device ROD Token Limits:
   Maximum Range Descriptors: 8
   Maximum Inactivity Timeout: 60 seconds
   Default Inactivity Timeout: 30 seconds
   Maximum Token Transfer Size: 524288
   Optimal Transfer Count: 524288

That maximum token transfer size [524288 blocks each 512 bytes gives 256 MB] is the largest size a ROD Token created by /dev/sdb can hold. Use that and show the --immed option on the destination:

 # ddptctl --pt=0x0,0x80000 --rtf=aa.rt /dev/sdb
 PT completes with a transfer count of 524288 [0x80000]

 # ddptctl --rtf=aa.rt --wut=0x0,0x80000 --immed /dev/sdc
 Started ODX Write Using Token command in immediate mode.
 User may need --list_id=257 on following invocation with --receive or
 --poll for completion

 # ddptctl --poll --rtf=aa.rt /dev/sdc
 RRTI for Write using token: Operation completed without errors
   transfer count of 524288 [0x80000]

To copy larger amounts and/or with a larger number of scatter gather elements (than 8 "range descriptors") use one of the four ODX variants in the ddpt utility.

Written by Douglas Gilbert.

Report bugs to <dgilbert at interlog dot com>.

Copyright © 2014-2021 Douglas Gilbert
This software is distributed under a FreeBSD license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

ddpt(8), ddpt_sgl(8)

ddpt(8), ddpt_sgl(8).