Provided by: nbdkit_1.24.1-2ubuntu4_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-torrent-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
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