iozone - Online in the Cloud

PROGRAM:

NAME

Iozone - Filesystem Benchmark

SYNOPSIS

Iozone [-a|-A] [-s filesize_Kb] [-r record_size_Kb] [-f [path]filename] [-i test] [-E]
[-p] [-m] [-M] [-t children] [-h] [-o] [-l min_number_procs] [-u max_number_procs] [-v]
[-R] [-x] [-d microseconds] [-F path1 path2...] [-V pattern ] [-j stride] [-T] [-C] [-B]
[-D] [-G] [-I] [-H depth] [-k depth] [-U mount_point] [-S cache_size] [-O] [-L line_size]
[-K] [-N] [-Q] [-P start_cpu] [-c] [-e] [-b Excel.xls] [-J milliseconds] [-X
[path]filename] [-Y [path]filename] [-w] [-W] [-z] [-Z] [-n min_filesize_Kb] [-g
max_filesize_Kb] [-y min_recordsize_Kb] [-q max_recordsize_Kb] [-+d] [-+u] [-+m
client_filename] [-+n] [-+N] [-+p percent_read] [-+r] [-+t] [-+l] [-+L] [-+D] [-+A
madvise_selector] [-+h hostname] [-+T] [-+w Percent de-dupable.]

DESCRIPTION

Iozone is a filesystem benchmark tool. The benchmark generates and measures a variety of
file operations. Iozone has been ported to many machines and runs under many operating
systems. This document will cover the many different types of operations that are tested
as well as coverage of all of the command line options.

Iozone is useful for determining a broad filesystem analysis of a vendor's computer
platform. The benchmark tests file I/O performance for the following operations.

Read, write, re-read, re-write, read backwards, read strided, fread, fwrite,
random read/write, pread/pwrite variants

While computers are typically purchased with an application in mind it is also likely that
over time the application mix will change. Many vendors have enhanced their operating
systems to perform well for some frequently used applications. Although this accelerates
the I/O for those few applications it is also likely that the system may not perform well
for other applications that were not targeted by the operating system. An example of this
type of enhancement is: Database. Many operating systems have tested and tuned the
filesystem so it works well with databases. While the database users are happy, the other
users may not be so happy as the entire system may be giving all of the system resources
to the database users at the expense of all other users. As time rolls on the system
administrator may decide that a few more office automation tasks could be shifted to this
machine. The load may now shift from a random reader application (database) to a
sequential reader. The users may discover that the machine is very slow when running this
new application and become dissatisfied with the decision to purchase this platform. By
using Iozone to get a broad filesystem performance coverage the buyer is much more likely
to see any hot or cold spots and pick a platform and operating system that is more well
balanced.

OPTIONS

-a Used to select full automatic mode. Produces output that covers all tested file
operations for record sizes of 4k to 16M for file sizes of 64k to 512M.

-A This version of automatic mode provides more coverage but consumes a bunch of time.
The -a option will automatically stop using transfer sizes less than 64k once the
file size is 32M or larger. This saves time. The -A option tells Iozone that you
are willing to wait and want dense coverage for small transfers even when the file
size is very large. NOTE: This option is deprecated in Iozone version 3.61. Use
-az -i 0 -i 1 instead.

-b filename
Used to specify a filename that will be used for output of an Excel compatible file
that contains the results.

-B Use mmap() files. This causes all of the temporary files being measured to be
created and accessed with the mmap() interface. Some applications prefer to treat
files as arrays of memory. These applications mmap() the file and then just access
the array with loads and stores to perform file I/O.

-c Include close() in the timing calculations. This is useful only if you suspect that
close() is broken in the operating system currently under test. It can be useful
for NFS Version 3 testing as well to help identify if the nfs3_commit is working
well.

-C Show bytes transferred by each child in throughput testing. Useful if your
operating system has any starvation problems in file I/O or in process management.

-d # Microsecond delay out of barrier. During the throughput tests all threads or
processes are forced to a barrier before beginning the test. Normally, all of the
threads or processes are released at the same moment. This option allows one to
delay a specified time in microseconds between releasing each of the processes or
threads.

-D Use msync(MS_ASYNC) on mmap files. This tells the operating system that all the
data in the mmap space needs to be written to disk asynchronously.

-e Include flush (fsync,fflush) in the timing calculations

-E Used to select the extension tests. Only available on some platforms. Uses pread
interfaces.

-f filename
Used to specify the filename for the temporary file under test. This is useful when
the unmount option is used. When testing with unmount between tests it is necessary
for the temporary file under test to be in a directory that can be unmounted. It is
not possible to unmount the current working directory as the process Iozone is
running in this directory.

-F filename filename filename ?
Specify each of the temporary file names to be used in the throughput testing. The
number of names should be equal to the number of processes or threads that are
specified.

-g # Set maximum file size (in Kbytes) for auto mode. One may also specify -g #k (size
in Kbytes) or -g #m (size in Mbytes) or -g #g (size in Gbytes). See -n for minimum
file size.

-G Use msync(MS_SYNC) on mmap files. This tells the operating system that all the data
in the mmap space needs to be written to disk synchronously.

-h Displays help screen.

-H # Use POSIX async I/O with # async operations. Iozone will use POSIX async I/O with
a bcopy from the async buffers back into the applications buffer. Some versions of
MSC NASTRAN perform I/O this way. This technique is used by applications so that
the async I/O may be performed in a library and requires no changes to the
applications internal model.

-i # Used to specify which tests to run. (0=write/rewrite, 1=read/re-read, 2=random-
read/write, 3=Read-backwards, 4=Re-write-record, 5=stride-read, 6=fwrite/re-fwrite,
7=fread/Re-fread, 8=mixed workload, 9=pwrite/Re-pwrite, 10=pread/Re-pread,
11=pwritev/Re-pwritev, 12=preadv/Re-preadv). One will always need to specify 0 so
that any of the following tests will have a file to measure. -i # -i # -i # is
also supported so that one may select more than one test.

-I Use DIRECT IO if possible for all file operations. Tells the filesystem that all
operations to the file are to bypass the buffer cache and go directly to disk. (not
available on all platforms)

-j # Set stride of file accesses to (# * record size). The stride read test will read
records at this stride.

-J # Millisecond delay before each I/O operation. This simulates the cpu compute cycle
of an application that precedes an I/O operation. One may also use -X or -Y to
control the compute cycle on a per I/O operation basis.

-k # Use POSIX async I/O (no bcopy) with # async operations. Iozone will use POSIX
async I/O and will not perform any extra bcopys. The buffers used by Iozone will be
handed to the async I/O system call directly.

-K Inject some random accesses in the testing.

-l # Set the lower limit on number of processes to run. When running throughput tests
this option allows the user to specify the least number of processes or threads to
start. This option should be used in conjunction with the -u option.

-L # Set processor cache line size to value (in bytes). Tells Iozone the processor cache
line size. This is used internally to help speed up the test.

-m Tells Iozone to use multiple buffers internally. Some applications read into a
single buffer over and over. Others have an array of buffers. This option allows
both types of applications to be simulated. Iozone´s default behavior is to re-use
internal buffers. This option allows one to override the default and to use
multiple internal buffers.

-M Iozone will call uname() and will put the string in the output file.

-n # Set minimum file size (in Kbytes) for auto mode. One may also specify -n #k (size
in Kbytes) or -n #m (size in Mbytes) or -n #g (size in Gbytes). See -g for maximum
file size.

-N Report results in microseconds per operation.

-o Writes are synchronously written to disk. (O_SYNC). Iozone will open the files
with the O_SYNC flag. This forces all writes to the file to go completely to disk
before returning to the benchmark.

-O Give results in operations per second.

-p This purges the processor cache before each file operation. Iozone will allocate
another internal buffer that is aligned to the same processor cache boundary and is
of a size that matches the processor cache. It will zero fill this alternate
buffer before beginning each test. This will purge the processor cache and allow
one to see the memory subsystem without the acceleration due to the processor
cache.

-P # Bind processes/threads to processors, starting with this cpu #. Only available on
some platforms. The first sub process or thread will begin on the specified
processor. Future processes or threads will be placed on the next processor. Once
the total number of cpus is exceeded then future processes or threads will be
placed in a round robin fashion.

-q # Set maximum record size (in Kbytes) for auto mode. One may also specify -q #k (size
in Kbytes) or -q #m (size in Mbytes) or -q #g (size in Gbytes). See -y for minimum
record size.

-Q Create offset/latency files. Iozone will create latency versus offset data files
that can be imported with a graphics package and plotted. This is useful for
finding if certain offsets have very high latencies. Such as the point where UFS
will allocate its first indirect block. One can see from the data the impacts of
the extent allocations for extent based filesystems with this option.

-r # Used to specify the record size, in Kbytes, to test. One may also specify -r #k
(size in Kbytes) or -r #m (size in Mbytes) or -r #g (size in Gbytes).

-R Generate Excel report. Iozone will generate an Excel compatible report to standard
out. This file may be imported with Microsoft Excel (space delimited) and used to
create a graph of the filesystem performance. Note: The 3D graphs are column
oriented. You will need to select this when graphing as the default in Excel is row
oriented data.

-s # Used to specify the size, in Kbytes, of the file to test. One may also specify
-s #k (size in Kbytes) or -s #m (size in Mbytes) or -s #g (size in Gbytes).

-S # Set processor cache size to value (in Kbytes). This tells Iozone the size of the
processor cache. It is used internally for buffer alignment and for the purge
functionality.

-t # Run Iozone in a throughput mode. This option allows the user to specify how many
threads or processes to have active during the measurement.

-T Use POSIX pthreads for throughput tests. Available on platforms that have POSIX
threads.

-u # Set the upper limit on number of processes to run. When running throughput tests
this option allows the user to specify the greatest number of processes or threads
to start. This option should be used in conjunction with the -l option.

-U mountpoint
Mount point to unmount and remount between tests. Iozone will unmount and remount
this mount point before beginning each test. This guarantees that the buffer cache
does not contain any of the file under test.

-v Display the version of Iozone.

-V # Specify a pattern that is to be written to the temporary file and validated for
accuracy in each of the read tests.

-w Do not unlink temporary files when finished using them.

-W Lock file when reading or writing.

-x Turn off stone-walling. Stonewalling is a technique used internally to Iozone. It
is used during the throughput tests. The code starts all threads or processes and
then stops them on a barrier. Once they are all ready to start then they are all
released at the same time. The moment that any of the threads or processes finish
their work then the entire test is terminated and throughput is calculated on the
total I/O that was completed up to this point. This ensures that the entire
measurement was taken while all of the processes or threads were running in
parallel. This flag allows one to turn off the stonewalling and see what happens.

-X filename
Used to specify a filename that will be used for the write telemetry information.
The file contains lines with offset, size, delay_in_milliseconds. Each of these
lines are used to perform an I/O operation. This is used when an application's
specific I/O operations are known, and one wishes to benchmark the system with this
specific application file behavior.

-y # Set minimum record size (in Kbytes) for auto mode. One may also specify -y #k (size
in Kbytes) or -y #m (size in Mbytes) or -y #g (size in Gbytes). See -q for maximum
record size.

-Y filename
Used to specify a filename that will be used for the read telemetry information.
The file contains lines with offset, size, delay_in_milliseconds. Each of these
lines are used to perform an I/O operation. This is used when an application's
specific I/O operations are known, and one wishes to benchmark the system with this
specific application file behavior.

-z Used in conjunction with -a to test all possible record sizes. Normally Iozone
omits testing of small record sizes for very large files when used in full
automatic mode. This option forces Iozone to include the small record sizes in the
automatic tests also.

-Z Enable mixing of mmap I/O and file I/O.

-+m filename
Used to specify a filename that will be used to specify the clients in a
distributed measurement. The file contains one line for each client. The fields are
space delimited. Field 1 is the client name. Field 2 is the working directory, on
the client, where Iozone will run. Field 3 is the path to the executable Iozone on
the client.

-+n No retests selected. Used to prevent retests from running.

-+N No truncating or deleting of previous test file before the sequential write test.
Useful only after -w is used in previous command to leave the test file in place
for reuse. This flag is of limited use, when a single retest is not enough, or to
easily control when sequential write retests occur without file truncation or
deletion.

-+u Used to enable CPU statistics collection.

-+d Diagnostic mode to troubleshoot a broken file I/O subsystem.

-+p percentage_reads
Used to set the percentage of threads/processes that will perform read testing in
the mixed workload test case.

-+r Enable O_RSYNC | O_SYNC on all testing.

-+l Enable byte range locking.

-+L Enable byte range locking & shared file mode.

-+D Enable O_DSYNC on all testing.

-+t Enable network performance test. Use with -+m

-+A# Enable madvise behavior. 0 = normal, 1=random, 2=sequential, 3=dontneed, 4=willneed

-+B Enable sequential mixed workload testing.

-+T Enable time stamps logging.

-+h Manually set hostname.

-+w# Percentage of data to be de-dupable between files.

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