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lmdd - move io for performance and debugging tests
lmdd [ option=value ] ...
lmdd copies a specified input file to a specified output with possible conversions. This program is primarily useful for timing I/O since it prints out the timing statistics after completing.
if=name Input file is taken from name; internal is the default. internal is a special file that acts like Sun's /dev/zero, i.e., it provides a buffer of zeros without doing a system call to get them. The following file names are taken to mean the standard input: -, 0, or stdin. of=name Output file is taken from name; internal is the default. internal is a special file that acts like /dev/null, without doing a system call to get rid of the data. The following file names are taken to mean the standard output: -, 1, or stdout. The following file names are taken to mean the standard error: 2, or stderr. bs=n Input and output block size n bytes (default 8192). Note that this is different from dd(1), it has a 512 byte default. Also note that the block size can be followed by 'k' or 'm' to indicate kilo bytes (*1024) or megabytes (*1024*1024), respectively. ipat=n If n is non zero, expect a known pattern in the file (see opat). Mismatches will be displayed as "ERROR: off=%d want=%x got=%x". The pattern is a sequence of 4 byte integers with the first 0, second 1, and so on. The default is not to check for the pattern. opat=n If n is non zero, generate a known pattern on the output stream. Used for debugging file system correctness. The default is not to generate the pattern. mismatch=n If n is non zero, stop at the first mismatched value. Used with ipat. skip=n Skip n input blocks before starting copy. fsync=n If n is non-zero, call fsync(2) on the output file before exiting or printing timing statistics. sync=n If n is non-zero, call sync(2) before exiting or printing timing statistics. rand=n This argument, by default off, turns on random behavior. The argument is not a flag, it is a size, that size is used as the upper bound for the seeks. Also note that the block size can be followed by 'k' or 'm' to indicate kilo bytes (*1024) or megabytes (*1024*1024), flush=n If n is non-zero and mmap(2) is available, call msync(2) to invalidate the output file. This flushes the file to disk so that you don't have unmount/mount. It is not as good as mount/unmount because it just flushes file pages - it misses the indirect blocks which are still cached. Not supported on all systems, compile time option. rusage=n If n is non-zero, print rusage statistics as well as timing statistics. Not supported on all systems, compile time option. count=n Copy only n input records.
This is the most common usage, the intent is to measure disk performance. The disk is a spare partition mounted on /spare. # mount /spare # lmdd if=internal of=/spare/XXX count=1000 fsync=1 7.81 MB in 3.78 seconds (2.0676 MB/sec) : Flush cache # umount /spare # mount /spare # lmdd if=/spare/XXX of=internal 7.81 MB in 2.83 seconds (2.7611 MB/sec)
Larry McVoy, firstname.lastname@example.org (c)1994 Larry McVoy $Date$ LMDD(8)