NAME

       nbdkit-sparse-random-plugin - make sparse random disks

SYNOPSIS

        nbdkit sparse-random [size=]SIZE [seed=SEED] [percent=N] [runlength=N]

DESCRIPTION

       "nbdkit-sparse-random-plugin" is a plugin for nbdkit(1) which makes disks containing sparse blocks of
       random data.  These disks have a similar shape to virtual machine disks, and this plugin can be used to
       benchmark disk copying tools like nbdcopy(1).  To get a non-sparse random disk, see
       nbdkit-random-plugin(1).

       The size of the virtual disk must be specified using the "size" parameter.  If you specify the "seed"
       parameter then you will get the same random data over multiple runs with the same seed.

       The "percent" parameter controls the percentage of the disk which contains random data versus sparse
       empty space.

       The plugin does not generate random data spread evenly over the disk.  Instead to make it look more like
       a real virtual machine disk, it tries to create runs of data and runs of empty space.  The "runlength"
       parameter controls the average length of each run of random data.

       The random data is generated using an insecure method.

   Writes and testing copying
       Writes to the disk verify that the data written is the same as the data read (if not, returning EIO).
       Thus when testing copies you can use a single instance of this plugin for both read and write:

        nbdkit -U - sparse-random size=1T --run 'nbdcopy "$uri" "$uri"'

       "qemu-img convert" could be used in place of nbdcopy.  See also nbdkit-checkwrite-filter(1).

PARAMETERS

       percent=N
           Specify  the approximate percentage of the disk which contains random data versus sparse empty space.
           The default is 10 (10%).  "percent=0" will create a completely  empty  disk  and  "percent=100"  will
           create a completely full disk.

       runlength=N
           Specify  the  average  length  of  runs  of  random  data.   This is expressed in bytes and the usual
           modifiers can be used.  The default is 16M, meaning that (on average) data runs will be 16  megabytes
           in length.

       seed=SEED
           Specify the random seed to get repeatable data over multiple runs.

           If not specified then a random seed is chosen.

       [size=]SIZE
           Specify the virtual size of the disk image.

           This parameter is required.

           "size=" is a magic config key and may be omitted in most cases.  See "Magic parameters" in nbdkit(1).

FILES

       $plugindir/nbdkit-sparse-random-plugin.so
           The plugin.

           Use "nbdkit --dump-config" to find the location of $plugindir.

VERSION

       "nbdkit-sparse-random-plugin" first appeared in nbdkit 1.24.

SEE ALSO

       nbdkit(1),   nbdkit-plugin(3),   nbdkit-data-plugin(1),   nbdkit-full-plugin(1),   nbdkit-null-plugin(1),
       nbdkit-pattern-plugin(1), nbdkit-random-plugin(1), nbdkit-zero-plugin(1), nbdcopy(1), qemu-img(1).

AUTHORS

       Richard W.M. Jones

COPYRIGHT

       Copyright (C) 2018 Red Hat Inc.

LICENSE

       Redistribution and use in source and binary forms, with or without modification, are  permitted  provided
       that the following conditions are met:

       •   Redistributions  of  source  code must retain the above copyright notice, this list of conditions and
           the following disclaimer.

       •   Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
           the following disclaimer in the documentation and/or other materials provided with the distribution.

       •   Neither the name of Red Hat nor the names of its contributors may  be  used  to  endorse  or  promote
           products derived from this software without specific prior written permission.

       THIS  SOFTWARE  IS  PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
       INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND  FITNESS  FOR  A  PARTICULAR
       PURPOSE  ARE  DISCLAIMED.  IN  NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
       INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,  PROCUREMENT  OF
       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
       ON  ANY  THEORY  OF  LIABILITY,  WHETHER  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
       DAMAGE.

nbdkit-1.24.1                                      2021-01-20                     nbdkit-sparse-random-plugin(1)