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NAME

nbdkit-nozero-filter - nbdkit nozero filter

SYNOPSIS

nbdkit --filter=nozero plugin [zeromode=MODE] [plugin-args...]

DESCRIPTION

nbdkit-nozero-filter is a filter that intentionally disables efficient handling of sparse file holes (ranges of all-zero bytes) across the NBD protocol. It is mainly useful for evaluating timing differences between naive vs. sparse-aware connections, and for testing client or server fallbacks.

PARAMETERS

zeromode=none|emulate

Optional, controls which mode the filter will use. Mode none (default) means that zero support is not advertised to the client; mode emulate means that zero support is emulated by the filter using the plugin's pwrite callback, regardless of whether the plugin itself implemented the zero callback with a more efficient way to write zeros.

EXAMPLES

Serve the file disk.img, but force the client to write zeroes explicitly rather than with NBD_CMD_WRITE_ZEROES:

nbdkit --filter=nozero file disk.img

Serve the file disk.img, allowing the client to take advantage of less network traffic via NBD_CMD_WRITE_ZEROES, but still forcing the data to be written explicitly rather than punching any holes:

nbdkit --filter=nozero file zeromode=emulate disk.img

SEE ALSO

nbdkit(1), nbdkit-file-plugin(1), nbdkit-filter(3).

AUTHORS

Eric Blake

COPYRIGHT

Copyright (C) 2018 Red Hat Inc.