nbdkit-sparse-random-plugin - Man Page

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

License

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

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.

Referenced By

nbdkit(1), nbdkit-checkwrite-filter(1), nbdkit-data-plugin(1), nbdkit-full-plugin(1), nbdkit-null-plugin(1), nbdkit-pattern-plugin(1), nbdkit-plugin(3), nbdkit-random-plugin(1), nbdkit-release-notes-1.24(1), nbdkit-zero-plugin(1).

2021-04-10 nbdkit-1.25.6