btrecord(8) — Linux manual page


BTRECORD(8)                                                  BTRECORD(8)

NAME         top

       btrecord - recreate IO loads recorded by blktrace

SYNOPSIS         top


       btrecord [ options ] <dev...>

DESCRIPTION         top

       The btrecord and btreplay tools provide the ability to record and
       replay IOs captured by the blktrace utility. Attempts are made to
       maintain ordering, CPU mappings and time-separation of IOs.

       The blktrace utility provides the ability to collect detailed
       traces from the kernel for each IO processed by the block IO
       layer. The traces provide a complete timeline for each IO
       processed, including detailed information concerning when an IO
       was first received by the block IO layer — indicating the device,
       CPU number, time stamp, IO direction, sector number and IO size
       (number of sectors). Using this information, one is able to
       replay the IO again on the same machine or another set up

       The basic operating work-flow to replay IOs would be something

           Run blktrace to collect traces. Here you specify the
           device or devices that you wish to trace and later replay IOs
         upon. Note:
           the only traces you are interested in are QUEUE requests —
           thus, to save system resources (including storage for
         traces), one could
           specify the -a queue command line option to blktrace.

           While blktrace is running, you run the workload that you
           are interested in.

           When the work load has completed, you stop the blktrace
           utility (thus saving all traces over the complete workload).

           You extract the pertinent IO information from the traces
         saved by
           blktrace using the btrecord utility. This will parse
           each trace file created by blktrace, and crafty IO
           to be used in the next phase of the workload processing.

           Once btrecord has successfully created a series of data
           files to be processed, you can run the btreplay utility which
           attempts to generate the same IOs seen during the sample
         workload phase.

OPTIONS         top

       -d <dir>
              Set input directory.  This option requires a single
              parameter providing the directory name for where input
              files are to be found. The default directory is the
              current directory (.).

       -D <dir>
              Set output directory.  This option requires a single
              parameter providing the directory name for where output
              files are to be found. The default directory is the
              current directory (.).

              Find trace files automatically This option instructs
              btreplay to go find all the trace files in the directory
              specified (either via the -d option, or in the default
              directory (.).

              Show help and exit.

              Show version number and exit.

       -m <nanoseconds>
              The -m option requires a single parameter which specifies
              an amount of time (in nanoseconds) to include in any one
              bunch of IOs that are to be processed. The smaller the
              value, the smaller the number of IOs processed at one time
              — perhaps yielding in more realistic replay.  However,
              after a certain point the amount of overhead per bunch may
              result in additional real replay time, thus yielding less
              accurate replay times.

              The default value is 10,000,000 nanoseconds (10

       -M <num>
              Set maximum number of packets per bunch.  The -M option
              requires a single parameter which specifies the maximum
              number of IOs to store in a single bunch. As with the -m
              option, smaller values may or may not yield more accurate
              replay times.

              The default value is 8, with a maximum value of up to 512
              being supported.

       -o <basename>
              Set base name for output files.  Each output file has 3

                  Device identifier (taken directly from the device name
                 of the
                  blktrace output file).

                  btrecord base name — by default ``replay''.

                  The CPU number (again, taken directly from the
                  blktrace output file name).

              This option requires a single parameter that will override
              the default name (replay), and replace it with the
              specified value.

              Enable verbose output.  This option will output some
              simple statistics at the end of a successful run.  Example
              output is:

              sdab:0: 580661 pkts (tot), 126030 pkts (replay), 89809 bunches, 1.4 pkts/bunch
              sdab:1: 2559775 pkts (tot), 430172 pkts (replay), 293029 bunches, 1.5 pkts/bunch
              sdab:2: 653559 pkts (tot), 136522 pkts (replay), 102288 bunches, 1.3 pkts/bunch
              sdab:3: 474773 pkts (tot), 117849 pkts (replay), 69572 bunches, 1.7 pkts/bunch

              The meaning of the columns is:

                   The first field contains the device name and CPU
                 identifier. Thus:
                   sdab:0: means the device sdab and traces on CPU 0.

                   The second field contains the total number of packets
                 processed for each
                   device file.

                   The next field shows the number of packets eligible
                 for replay.

                   The fourth field contains the total number of IO

                   The last field shows the average number of IOs per
                 bunch recorded.

AUTHORS         top

       btrecord was written by Alan D. Brunelle.  This man page was
       created from the btreplay documentation by Bas Zoetekouw.

REPORTING BUGS         top

       Report bugs to <>

COPYRIGHT         top

       Copyright © 2007 Alan D. Brunelle, Alan D. Brunelle and Nathan
       This is free software.  You may redistribute copies of it under
       the terms of the GNU General Public License
       <>.  There is NO WARRANTY, to
       the extent permitted by law.
       This manual page was created for Debian by Bas Zoetekouw.  It was
       derived from the documentation provided by the authors and it may
       be used, distributed and modified under the terms of the GNU
       General Public License, version 2.
       On Debian systems, the text of the GNU General Public License can
       be found in /usr/share/common-licenses/GPL-2.

SEE ALSO         top

       The full documentation for btreplay can be found in
       /usr/share/doc/blktrace on Debian systems.
       blktrace(8), blkparse(1), btreplay(8)

COLOPHON         top

       This page is part of the blktrace (Linux block layer I/O tracer)
       project.  Information about the project can be found at [unknown
       -- if you know, please contact] It is not
       known how to report bugs for this man page; if you know, please
       send a mail to  This page was obtained from
       the project's upstream Git repository
       on 2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-12.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

blktrace git-20071207142532 December  8, 2007                BTRECORD(8)

Pages that refer to this page: btreplay(8)