DOKK / manpages / debian 10 / nbdkit / nbdkit-nozero-filter.1.en
nbdkit-nozero-filter(1) NBDKIT nbdkit-nozero-filter(1)

nbdkit-nozero-filter - nbdkit nozero filter

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

"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.

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.

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

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

Eric Blake

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2019-01-26 nbdkit-1.10.3