1mbuffer(1) console utility mbuffer(1)
2
6 mbuffer - measuring buffer
7
9 mbuffer [options]
10
12 mbuffer buffers i/o operations and displays the throughput rate. It is
13 multithreaded, supports network connections, and offers more options
14 than the standard buffer.
15
17 -i <filename>
18 use filename as input instead of the standard input (needs to be
19 given for multi volume support)
20 -I <port>
22 use network port port as input instead of the standard input. If
23 given a hostname and a port in the form hostname:port the first
24 interface with the IP of hostname will be used.
25 -o <filename>
27 use filename as output instead of the standard output (needs to
28 be given for multi volume support, will enable use of sendfile
29 if available)
30 -O <hostname:port>
32 write output to hostname:port instead of the standard output
33 (will enable use of sendfile if available)
34 -b <num>
36 use num blocks for buffer (default 256)
37 -s <size>
39 use blocks of size bytes for buffer (default 10240)
40 -m <size>
42 use a total of size bytes for buffer (default 2MB) - size can be
43 set with a trailing character (b and B for Byte, k for kByte, M
44 for MByte, G for Gigabyte, and with % for a percentage of total
45 physical memory)
46 -L lock buffer in memory - this option is not available for file-
48 based buffers and requires mbuffer to be setuid root (use with
49 care)
50 -n <num>
52 num volumes in input device (requires use of option -i for input
53 device specification) [currently multi volume support is EXPERI‐
54 MENTAL]
55 -t use a memory mapped temporaray file as buffer (use with huge
57 buffers)
58 -T <file>
60 as -t but use file instead
61 -d use blocksize of device for output (needed for some devices,
63 slows output down)
64 -D <size>
66 assume an output volume of size bytes (default infinite) after
67 which a volume change will be initiated. Small values are useful
68 for the timely testing of multi-volume runs; accurate values if
69 your device doesn't properly signal end of media. Size can be
70 set with a trailing character (b and B for Byte, k for kByte, M
71 for MByte, or G for Gigabyte)
72 -P <num>
74 start writing after the buffer has been filled to num% (default
75 0 - start at once)
76 -p <num>
78 start reading after the buffer has dropped below fillratio of
79 num% (default 100 - start at once)
80 -l <file>
82 log messages to file instead of standard error output
83 -u <num>
85 pause num microseconds after each write - might increase perfor‐
86 mance on some drives with very low performace (< 1 MB/sec)
87 -r <rate>
89 Set the maximum read rate to <rate>. <rate> can be given in
90 either Bytes, kBytes, MBytes, or GBytes per second. To do so,
91 use an apropriate suffix (i.e. k,M,G). This options is useful if
92 you have a tape that is capable to transfer data faster than the
93 host can handle it. In this case you can use this option to
94 limit the transfer rate and keep the tape running. Be aware that
95 this is both good for your tape drive, and enhances overall per‐
96 formance, by avoiding tape screwing.
97 -R <rate>
99 Same as above only for setting the transfer limit for the
100 writer.
101 -A <cmd>
103 used devices is an autoloader which uses cmd to load the next
104 volume
105 -a <time>
107 used device is an autoloader which takes time seconds to load a
108 new tape
109 -f overwrite output file if it exists already
111 -c write with synchronous data integrity support - This option
113 forces all writes to complete before continuing. This enables
114 errors to be reported earlier and more precisely, but might
115 decrease performance. Especially systems with high level of data
116 integrity support suffer a huge performance hit. Others might
117 seem to be unaffected, but just neglect support for full syn‐
118 chronous data integrity.
119 -v <num>
121 set verbose level to num. Valid values are 0..5 (0 = none, 1 =
122 errors, 2 = warnings, 4 = informations, 5 = debugging informa‐
123 tions). Higher values include lower values messages.
124 -q quiet - do not display the status on the standard error output
126 -h, --help
128 Output help information and exit.
129 -H, --md5
131 Generate md5 hash of transfered data.
132 -V, --version
134 Output version information and exit.
135
137 If TMPDIR is set, mbuffer allocates storage for file based buffers in
138 this directory. If TMPDIR is unset /var/tmp will be used.
139
141 /bin/mbuffer
142 /var/tmp/mbuffer-*
143
145 To run this program with the default options just type:
146 mbuffer
148 Using mbuffer to do a backup with tar to the default tape device.
150 Options for this example: memory mapped temporary file with a size of
151 10 Megabytes, start after 80% of the buffer have been filled.
152 tar cf - mydirectory | gzip | mbuffer -t -m 10M -p 80 -f -o $TAPE
154 Using mbuffer with 3 tapes for input and extracting the contents in the
156 current work directory:
157 mbuffer -n 3 -i $TAPE | gzip -dc | tar xf -
159 Using mbuffer to write to multiple tape volumes:
161 tar cf - /usr | mbuffer -f -o $TAPE
163 Write to multiple tapes and erase every tape before writing:
165 tar cf - /usr | mbuffer -A "echo next tape; read a < /dev/tty; mt erase
167 $TAPE" -f -o $TAPE
168 Making a backup via network:
170 tape server: mbuffer -I 8000 -f -o $TAPE
172 backup client: tar zcf - /home | mbuffer -O tapeserver:8000
174
176 Thomas Maier-Komor <software@maier-komor.de>
177
180 buffer(1), gpl(7)
181Thomas Maier-Komor 20070502 mbuffer(1)