btreplay(8) — Linux manual page


BTREPLAY(8)                                                  BTREPLAY(8)

NAME         top

       btreplay - recreate IO loads recorded by blktrace

SYNOPSIS         top

       btreplay [ 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

       -c <num>
              Set number of CPUs to use.

       -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 (.).

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

              Show help and exit.

       -i <basename>
              Set base name for input files.  Each input 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.

       -I <num>
              Set number of iterations to run.  This option requires a
              single parameter which specifies the number of times to
              run through the input files. The default value is 1

       -M <filename>
              Specify device mappings.  This option requires a single
              parameter which specifies the name of a file contain
              device mappings. The file must be very simply managed,
              with just two pieces of data per line:

                  The device name on the recorded system (with the
                  removed). Example: /dev/sda would just be sda.

                  The device name on the replay system to use (again,
                without the
                  '/dev/' path prepended).

              An example file for when one would map devices /dev/sda
              and /dev/sdb on the recorded system to dev/sdg and sdh on
              the replay system would be:

                     sda sdg
                     sdb sdh

              The only entries in the file that are allowed are these
              two element lines — we do not (yet?) support the notion of
              blank lines, or comment lines, or the like.

              The utility allows for multiple -M options to be supplied
              on the command line.

              Disable pre-bunch stalls.  When specified on the command
              line, all pre-bunch stall indicators will be ignored. IOs
              will be replayed without inter-bunch delays.

       -x <factor>
              Specify acceleration factor. Default value is 1 (no

              Enable verbose output.  When specified on the command
              line, this option instructs btreplay to store information
              concerning each stall and IO operation performed by
              btreplay. The name of each file so created will be the
              input file name used with an extension of .rep appended
              onto it. Thus, an input file of the name sdab.replay.3
              would generate a verbose output file with the name
              sdab.replay.3.rep in the directory specified for input

              In addition, btreplay will also output to stderr the names
              of the input files being processed.

              Show version number and exit.

              Enable writing during replay.  As a precautionary measure,
              by default btreplay will not process write requests. In
              order to enable btreplay to actually write to devices one
              must explicitly specify the -W option.

AUTHORS         top

       btreplay 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), btrecord(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                BTREPLAY(8)

Pages that refer to this page: btrecord(8)