Tuesday, August 17, 2010

IOZONE examples


User contributed tutorial written by Ramesh Natarajan.

Following are few situations where you may be interested in performing a filesystem benchmarking.

=> Deploying a new application that is very read and write intensive.
=> Purchased a new storage system and would like to measure the performance.
=> Changing the RAID level and would like to measure the performance of the new RAID.
=> Changing the storage parameters and would like to know the performance impact of this change

This article gives you a jumpstart on performing benchmark on filesystem using iozone a free Filesystem Benchmark utility.

1. Download and Install iozone software

Go to iozone and download the iozone for your appropriate platform. I downloaded the "Linux i386 RPM". Install the iozone from the RPM as shown below. By default this installs the iozone under /opt/iozone/bin
# cd /tmp
# wget http://www.iozone.org/src/current/iozone-3-303.i386.rpm
# rpm -ivh iozone-3-303.i386.rpm

Sample output:

Preparing...                ########################################### [100%]
1:iozone ########################################### [100%]

Note: You can install iozone under any UNIX / Linux or Windows operating system.

2. Start the performance test

Execute the following command in the background to begin the performance test.

# /opt/iozone/bin/iozone -R -l 5 -u 5 -r 4k -s 100m -F /home/f1 /home/f2 /home/f3 /home/f4 /home/f5 | tee -a /tmp/iozone_results.txt &

Let us review all the individual parameter passed to iozone command.

  • -R : Instructs the iozone to generate excel compatible text output.
  • -l : This is the lower limit on how many process/threads needs to be started by iozone during execution. In this example, iozone will start 5 threads.
  • -u : This is the upper limit on how many process/threads needs to be started by iozone during execution. In this example, iozone will not exceed maximum of 5 threads. If you set -l and -u to the same value, it will run exactly those many number of process/threads. In this example, this will execute exactly 5 threads.
  • -r : This specifies the record size. In this example, the record size for benchmark testing is 4k. This is an important parameter to be set appropriately depending on the purpose of your filesystem performance testing. For e.g. If you are performing benchmark on a filesystem that will host a database, it is appropriate to set this value to the DB block size of the database.
  • -s : This specifies the size of the file that needs to be tested. In this example, iozone will try to perform test on 100Mb file.
  • -F : Specify the temporary filename that should be used by the iozone during testing. The total number of files specified here should match the value specified in -l and -u parameter.

3. Analyze the output of iozone file.

The first part of the output will contain the details about every individual filesystem performance metrics that was tested. for e.g. Initial write, rewrite etc as shown below.

        Iozone: Performance Test of File I/O
Version $Revision: 3.303 $
Compiled for 32 bit mode.
Build: linux

Contributors:William Norcott, Don Capps, Isom Crawford, Kirby Collins
Al Slater, Scott Rhine, Mike Wisner, Ken Goss
Steve Landherr, Brad Smith, Mark Kelly, Dr. Alain CYR,
Randy Dunlap, Mark Montague, Dan Million,
Jean-Marc Zucconi, Jeff Blomberg, Benny Halevy,
Erik Habbinga, Kris Strecker, Walter Wong, Joshua Root.

Run began: Thu Jun 22 00:08:51 2008

Excel chart generation enabled
Record Size 4 KB
File size set to 102400 KB
Command line used: /opt/iozone/bin/iozone -R -l 5 -u 5 -r 4k -s 100m -F /home/f1 /home/f2 /home/f3 /home/f4 /home/f5
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
Min process = 5
Max process = 5
Throughput test with 5 processes
Each process writes a 102400 Kbyte file in 4 Kbyte records

Children see throughput for 2 initial writers = 60172.28 KB/sec
Parent sees throughput for 2 initial writers = 45902.89 KB/sec
Min throughput per process = 28564.52 KB/sec
Max throughput per process = 31607.76 KB/sec
Avg throughput per process = 30086.14 KB/sec
Min xfer = 92540.00 KB

Children see throughput for 2 rewriters = 78658.92 KB/sec
Parent sees throughput for 2 rewriters = 34277.52 KB/sec
Min throughput per process = 35743.92 KB/sec
Max throughput per process = 42915.00 KB/sec
Avg throughput per process = 39329.46 KB/sec
Min xfer = 85296.00 KB

Similar values like above will be generated for readers, re-readers, reverse readers, stride readers, random readers, mixed workload, random writers, pwrite writers, pread readers. The last part of the iozone output will contain the Throughput summary for different metrics as shown below.

Throughput report Y-axis is type of test X-axis is number of processes
Record size = 4 Kbytes
Output is in Kbytes/sec

Initial write 60172.28
Rewrite 78658.92
Read 2125613.88
Re-read 1754367.31
Reverse Read 1603521.50
Stride read 1633166.38
Random read 1583648.75
Mixed workload 1171437.78
Random write 5365.59
Pwrite 26847.44
Pread 2054149.00

(Fig.01: iozone in action)

Iozone does a benchmarking on different types of file system performance metrics. for e.g. Read, Write, Random read. Depending on the application that you are planning to deploy on that particular filesystem, pay attention to the appropriate items. for e.g. If the filesystem hosts an read intensive OLTP database, then pay attention to Random Read, Random write and Mixed workload. If the application does lot of streaming media content, pay attention to the Sequential Read. On a final note, you can generate graphs using the Generate_Graphs and gengnuplot.sh located under /opt/iozone/bin, based on the iozone output.


  • Iozone PDF documentation – Full documentation from iozone.org explaining all the iozone command line options and more.
  • Linux Iozone graph example - This is a sample *.xls file from iozone that shows the kind of excel output that can be generated from iozone.

This article was written by Ramesh Natarajan. At the The Geek Stuff blog he shares his knowledge and experience on Linux and other Geeky stuff. He has more than 15 years of experience in IT industry and has performed very intensive work on Linux system administration, DBA, Hardware and Storage. nixCraft welcomes readers' tips / howtos.

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