Provided by: nbdkit_1.16.2-1ubuntu3_amd64 bug

NAME
       nbdkit-readahead-filter - prefetch data when reading sequentially


SYNOPSIS
        nbdkit --filter=readahead plugin


DESCRIPTION
       "nbdkit-readahead-filter" is a filter that prefetches data when the client is reading sequentially.

       A common use for this filter is to accelerate sequential copy operations (like "qemu-img convert") when
       plugin requests have a high overhead (like nbdkit-curl-plugin(1)).  For example:

        nbdkit -U - --filter=readahead curl https://example.com/disk.img \
               --run 'qemu-img convert $nbd disk.img'

       The filter uses a simple adaptive algorithm which accelerates sequential reads, but has a small penalty
       if the client does random reads.  If the client mixes reads with writes or write-like operations
       (trimming, zeroing) then it will work but there can be a large performance penalty.


PARAMETERS
       There are no parameters specific to nbdkit-readahead-filter.  Any parameters are passed through to and
       processed by the underlying plugin in the normal way.


FILES
       $filterdir/nbdkit-readahead-filter.so
           The filter.

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


VERSION
       "nbdkit-readahead-filter" first appeared in nbdkit 1.12.


SEE ALSO
       nbdkit(1), nbdkit-cache-filter(1), nbdkit-curl-plugin(1), nbdkit-retry-filter(1), nbdkit-ssh-plugin(1),
       nbdkit-vddk-plugin(1), nbdkit-filter(3), qemu-img(1).


AUTHORS
       Richard W.M. Jones


COPYRIGHT
       Copyright (C) 2019 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,
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