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IOZONE(1)              DragonFly General Commands Manual             IOZONE(1)


NAME

     iozone - Performance Test of Sequential File I/O


SYNOPSIS

     iozone [megabytes] [record_length_in_bytes] [[path]filename]
     iozone auto[=filename]
     iozone raw[=filename]
     iozone cdrom[=filename]
     iozone help


DESCRIPTION

       Copyright 1991, 1992, 1994   William D. Norcott

       License to freely use and distribute this software is hereby granted
       by the author, subject to the condition that this copyright notice
       remains intact.  The author retains the exclusive right to publish
       derivative works based on this work, including, but not limited to,
       revised versions of this work

       This test writes a X MEGABYTE sequential file in Y byte chunks, then
       rewinds it  and reads it back.  [The size of the file should be
       big enough to factor out the effect of any disk cache.].  Finally,
       IOZONE deletes the temporary file

       The file is written (filling any cache buffers), and then read.  If the
       cache is >= X MB, then most if not all the reads will be satisfied from
       the cache.  However, if it is less than or equal to .5X MB, then NONE
     of
       the reads will be satisfied from the cache.  This is becase after the
       file is written, a .5X MB cache will contain the upper .5 MB of the
     test
       file, but we will start reading from the beginning of the file (data
       which is no longer in the cache)

       In order for this to be a fair test, the length of the test file must
       be AT LEAST 2X the amount of disk cache memory for your system.  If
       not, you are really testing the speed at which your CPU can read blocks
       out of the cache (not a fair test)

       IOZONE does not normally test the raw I/O speed of your disk or system.
       It tests the speed of sequential I/O to actual files.  Therefore, this
       measurement factors in the efficiency of you machines file system,
       operating system, C compiler, and C runtime library.  It produces a
       measurement which is the number of bytes per second that your system
       can read or write to a file.

       You use IOZONE to test the I/O speed of a UNIX 'RAW DEVICE' such
       as a tape drive, hard disk drive, floppy disk drive, etc.  To do this,
       you must define the symbol NO_DELETE when you compile IOZONE.  If you
       fail to define NO_DELETE, IOZONE will treat the raw device as a
       temporary file, and WILL DELETE THE RAW DEVICE after the test
     completes!
       When testing raw devices, any UNIX buffer caching is bypassed.  IOZONE
       still is using the read()/write() system calls, so you are not quite
       testing the device at the low level of say, disk controller
     diagnostics.
       On the other hand, that kind of testing is highly system- and device-
       specific, and my goal for IOZONE has been to build a highly portable
       benchmark -- not one which is tied to a particular operating system or
       hardware configuration.  In practice, I have tested raw disk and tape
       peripherals and the results are very close to the manufacturer's specs
       for those devices.


AUTHOR

     Bill Norcott

                         Sun Aug 30 06:34:29 UTC 2015

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