BTREPLAY(8)															       BTREPLAY(8)

NAME

       btreplay - recreate IO loads recorded by blktrace

SYNOPSIS

       btreplay [ options ] <dev...>

DESCRIPTION

       The  btrecord  and btreplay tools provide the ability to record and replay IOs captured by the blktrace utility. Attempts are made to main-
       tain 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 entirely.

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

       -
	   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 descriptions
	   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

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

       -d <dir>
       --input-directory=<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 (.).

       -F
       --find-records
	      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 (.).

       -h
       --help
	      Show help and exit.

       -i <basename>
       --input-base=<basename>
	      Set base name for input files.  Each input file has 3 fields:

	      1.
		  Device identifier (taken directly from the device name of the
		  blktrace output file).

	      2.
		  btrecord base name -- by default ``replay''.

	      3.
		  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>
       --iterations=<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>
       --map-devs=<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 '/dev/'
		  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.

       -N
       --no-stalls
	      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.

       -v
       --verbose
	      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 files.

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

       -V
       --version
	      Show version number and exit.

       -W
       --write-enable
	      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

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

REPORTING BUGS

       Report bugs to <linux-btrace@vger.kernel.org>

COPYRIGHT

       Copyright (C) 2007 Alan D. Brunelle, Alan D. Brunelle and Nathan Scott.
       This  is  free  software.   You	 may   redistribute   copies   of   it	 under	 the   terms   of   the   GNU	General   Public   License
       <http://www.gnu.org/licenses/gpl.html>.	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

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

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