1nbdkit-readahead-filter(1)          NBDKIT          nbdkit-readahead-filter(1)
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NAME

6       nbdkit-readahead-filter - prefetch data when reading sequentially
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SYNOPSIS

9        nbdkit --filter=readahead plugin
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DESCRIPTION

12       "nbdkit-readahead-filter" is a filter that prefetches data when the
13       client is reading sequentially.
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15       A common use for this filter is to accelerate sequential copy
16       operations (like "qemu-img convert") when plugin requests have a high
17       overhead (like nbdkit-curl-plugin(1)).  For example:
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19        nbdkit -U - --filter=readahead curl https://example.com/disk.img \
20               --run 'qemu-img convert $nbd disk.img'
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22       If you use this filter with clients that have a random access pattern
23       it will slow everything down.
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PARAMETERS

26       There are no parameters specific to nbdkit-readahead-filter.  Any
27       parameters are passed through to and processed by the underlying plugin
28       in the normal way.
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SEE ALSO

31       nbdkit(1), nbdkit-cache-filter(1), nbdkit-curl-plugin(1),
32       nbdkit-ssh-plugin(1), nbdkit-vddk-plugin(1), nbdkit-filter(3),
33       qemu-img(1).
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AUTHORS

36       Richard W.M. Jones
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39       Copyright (C) 2019 Red Hat Inc.
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LICENSE

42       Redistribution and use in source and binary forms, with or without
43       modification, are permitted provided that the following conditions are
44       met:
45
46       ·   Redistributions of source code must retain the above copyright
47           notice, this list of conditions and the following disclaimer.
48
49       ·   Redistributions in binary form must reproduce the above copyright
50           notice, this list of conditions and the following disclaimer in the
51           documentation and/or other materials provided with the
52           distribution.
53
54       ·   Neither the name of Red Hat nor the names of its contributors may
55           be used to endorse or promote products derived from this software
56           without specific prior written permission.
57
58       THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
59       EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
60       IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
61       PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
62       LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
63       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
64       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
65       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
66       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
67       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
68       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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72nbdkit-1.12.3                     2019-05-21        nbdkit-readahead-filter(1)
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