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.

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.

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