BTRECORD(8)															       BTRECORD(8)

NAME

       btrecord - recreate IO loads recorded by blktrace

SYNOPSIS

       Usage:

       btrecord [ 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

       -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 (.).

       -D <dir>
       --output-directory=<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 (.).

       -F
       --find-traces
	      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 (.).

       -h
       --help
	      Show help and exit.

       -V
       --version
	      Show version number and exit.

       -m <nanoseconds>
       --max-bunch-time=<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 realis-
	      tic replay.  However, after a certain point the amount of overhead per bunch may result in additional real replay time, thus  yield-
	      ing less accurate replay times.

	      The default value is 10,000,000 nanoseconds (10 milliseconds).

       -M <num>
       --max-pkts=<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>
       --output-base=<basename>
	      Set base name for output files.  Each output 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.

       -v
       --verbose
	      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:

	      1.
		   The first field contains the device name and CPU identifier. Thus:
		   sdab:0: means the device sdab and traces on CPU 0.

	      2.
		   The second field contains the total number of packets processed for each
		   device file.

	      3.
		   The next field shows the number of packets eligible for replay.

	      4.
		   The fourth field contains the total number of IO bunches.

	      5.
		   The last field shows the average number of IOs per bunch recorded.

AUTHORS

       btrecord 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), btreplay (8)

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