Lustre 1.6 Operations Manual

Offset(o):
Distance between two successive regions when all threads are writing to the same
file. In the case of multiple files, threads start writing in files at Offset bytes.
Parameter
--chunknoise = N
--chunksize = N[,N2,N3...]
--chunksize_low=L
--chunksize_high=H
--chunksize_incr=F
--cleanup
--directio
--posixio
--cowio
--offset=O[,O2,O3...]
--offset_low=OL
--offset_high=OH
--offset_inc=PH
--prerun=”pre-command”
--postrun=”postcommand”
--regioncount=N[,N2,N3...]
Description
N is a byte specifier. When performing an I/O task, add a
random signed integer in the range [-N,N] to the chunksize.
All regions are still fully written. This randomizes the I/O
size to some extent.
N is a byte specifier and performs I/O in chunks of N kilo-,
mega-, giga- or terabyte. You can give a comma separated list
of multiple values. This argument is mutually exclusive with -
-chunksize_low. Note that each thread allocates a buffer of
size chunksize + chunknoise for use during the run.
Performs a sequence of operations starting with a chunksize
of L, increasing it by F% each time until chunksize exceeds H.
Removes files that were created during the run. If there is an
encounter for existing files, they are over-written.
One of these arguments must be passed to indicate if
DIRECT I/O, POSIX I/O or COW I/O is used.
The argument is a byte specifier or a list of specifiers. Each
run uses regions at offset multiple of O in a single file. If the
run targets multiple files, then the I/O writes at offset O in
each file.
The arguments are byte specifiers. They generate runs with a
range of offsets starting at OL, increasing P% until the region
size exceeds OH. Each of these arguments is exclusive with
the offset argument.
Before each run, executes the pre-command as a shell
command through the system(3) call. The timestamp of the
run is appended as the last argument to the pre-command
string. Typically, this is used to clear statistics or start a data
collection script when the run starts.
After each run, executes the post-command as a shell
command through the system(3) call. The timestamp of the
run is appended as the last argument to the pre-command
string. Typically, this is used to append statistics for the run or
close an open data collection script when the run completes.
PIOS writes to N regions in a single file or block device or to
N files.
19-14 Lustre 1.6 Operations Manual • September 2008