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] [-+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.
-+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.
AUTHOR
Original Author: William D. Norcott. wnorcott@us.oracle.com
Features & extensions: Don Capps capps@iozone.org