1nbdkit-rate-filter(1) NBDKIT nbdkit-rate-filter(1)
2
6 nbdkit-rate-filter - limit bandwidth by connection or server
7
9 nbdkit --filter=rate PLUGIN [PLUGIN-ARGS...]
10 [rate=BITSPERSEC]
11 [connection-rate=BITSPERSEC]
12 [rate-file=FILENAME] [connection-rate-file=FILENAME]
13
15 "nbdkit-rate-filter" is a filter that limits the bandwidth that can be
16 used by the server. Limits can be applied per connection and/or for
17 the server as a whole.
18
20 nbdkit --filter=rate memory size=64M rate=1M
21 Create a 64M RAM disk and limit server bandwidth as a whole to a
22 maximum of 1 Mbps (megabit per second).
23 nbdkit --filter=rate memory size=64M connection-rate=50K
25 Limit each connection to 50 Kbps (kilobits per second). However as
26 there is no limit to the number of simultaneous connections this
27 does not limit overall server bandwidth.
28 nbdkit --filter=rate memory size=64M connection-rate=50K rate=1M
30 Limit each connection to 50 Kbps. Additionally the total bandwidth
31 across all connections to the server is limited to 1 Mbps.
32 nbdkit --filter=rate memory size=64M rate=1M rate-file=/tmp/rate
34 Initially limit bandwidth to 1 Mbps. While the server is running
35 the rate can be adjusted dynamically by writing a different rate
36 into /tmp/rate.
37
39 connection-rate=BITSPERSEC
40 Limit each connection to "BITSPERSEC".
41 rate=BITSPERSEC
43 Limit total bandwidth across all connections to "BITSPERSEC".
44 connection-rate-file=FILENAME
46 rate-file=FILENAME
47 Adjust the per-connection or total bandwidth dynamically by writing
48 "BITSPERSEC" into "FILENAME". See "DYNAMIC ADJUSTMENT" below.
49 "BITSPERSEC" can be specified as a simple number, or you can use a
51 number followed by "K", "M" etc to mean kilobits, megabits and so on.
52
54 Using the "connection-rate-file" or "rate-file" parameters you can
55 dynamically adjust the bandwidth while the server is running.
56 If the file is not present when the server starts up then the initial
58 rate is taken from the associated "connection-rate" or "rate" parameter
59 (or if that is not present, then it is unlimited). If the file is
60 deleted while the server is running then the last rate read from the
61 file continues to be used.
62 The file should be updated atomically (eg. create a new file, then
64 rename or mv(1) the new file over the old file).
65 There will be a short delay between the file being updated and the new
67 rate coming into effect.
68
70 You can specify "rate" and "connection-rate" on their own or together.
71 If you specify neither, the filter is turned off.
72 The rate filter approximates the bandwidth used by the NBD protocol on
74 the wire. Some operations such as zeroing and trimming are effectively
75 free (because only a tiny NBD message is sent over the network) and so
76 do not count against the bandwidth limit. NBD and TCP protocol
77 overhead is not included, so you may find that other tools such as
78 tc(8) and iptables(8) give more accurate results.
79 There are separate bandwidth limits for read and write (ie. download
81 and upload to the server).
82 If the size of requests made by your client is much larger than the
84 rate limit then you can see long, lumpy sleeps in this filter. In the
85 future we may modify the filter to break up large requests
86 automatically in order to limit the length of sleeps. Placing the
87 nbdkit-blocksize-filter(1) in front of this filter may help in the
88 meantime.
89
91 nbdkit(1), nbdkit-blocksize-filter(1), nbdkit-delay-filter(1),
92 nbdkit-filter(3), iptables(8), tc(8).
93
95 Richard W.M. Jones
96
98 Copyright (C) 2019 Red Hat Inc.
99
101 Redistribution and use in source and binary forms, with or without
102 modification, are permitted provided that the following conditions are
103 met:
104 · Redistributions of source code must retain the above copyright
106 notice, this list of conditions and the following disclaimer.
107 · Redistributions in binary form must reproduce the above copyright
109 notice, this list of conditions and the following disclaimer in the
110 documentation and/or other materials provided with the
111 distribution.
112 · Neither the name of Red Hat nor the names of its contributors may
114 be used to endorse or promote products derived from this software
115 without specific prior written permission.
116 THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY
118 EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
119 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
120 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE
121 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
122 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
123 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
124 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
125 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
126 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
127 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
128nbdkit-1.12.3 2019-05-21 nbdkit-rate-filter(1)