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Name

lmdd - move io for performance and debugging tests

Synopsis

lmdd [ option=value ] ...

Description

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.

Options

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.
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.
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.

Examples

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)

Author

Larry McVoy, lm@sun.com
Not copyrighted.

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