DISKSPEED - hard disk speed test

Download disksped.exe (54,784 bytes), download source code diskspeed.cpp (9,232 bytes).

DISKSPEED is a program to measure hard disk throughput and CPU load in disk transactions under Windows 95 and Windows NT operating systems. These numbers may be needed to optimize system performance for such applications as video capture/playback and multichannel sound recording/playback.

The program can be run by the following command line:

DISKSPED <test file size> <test file location>

Here optional <test file size> specifies size of data to read/write in megabytes (default is 64), <test file location> - device letter and folder where to place the test file (default is C:\). For example:

DISKSPED 256 d:

The program works in the following sequence:

  1. Test file of zero length is created.
  2. The file is filled with pseudorandom data until specified size is reached, with cache disabled. This time, "New File Write Speed" is measured.
  3. The file is rewritten with test data, with cache disabled. This time "Uncached Write Speed" is measured.
  4. Thet file is read from begin to end with cache disabled, while "Uncached Read Speed" is measured.
  5. The file is rewritten with test data, with cache enabled. This time "Cached Write Speed" is measured.
  6. The file is read from begin to end with cache enabled, while "Cached Read Speed" is measured.

Read/write speed is calculated as file size divided by elapsed time.

On every test stage the program also measures CPU load, this means how much of CPU clocks the disk operations take. To measure the load, low priority execution thread is started. The thread consists of an empty loop which counts number of its passes. The thread speed is measured before all disk tests. The difference between anticipated and real loop pass count allows to calcalate how much time was eaten by disk I/O.

Maximum sequential read/write speed and minimum CPU load are usually achieved with file cache disabled. To disable cache, the program opens the test file in FILE_FLAG_NO_BUFFERING and FILE_FLAG_WRITE_THROUGH modes. To further increase I/O speed, the program accesses last byte of a test file, thus preloading FAT chain in disk cache. With cache enabled, I/O speed is usually lower, because read/written data flush cached FAT out of cache, thus making FAT being read again. The lowest speed is obtained when a new file is written.

In DMA (Bus Master) mode, CPU load should be less than 10%. If 40-60% load is measured, your disk is working in PIO mode.

If write speed is much lower that read speed, write-back caching is disabled in your disk drive (not in the system). I don't know how to fix it yet. Some SCSI disks have a jumper or software to control write caching.

Download disksped.exe (54,784 bytes), download source code diskspeed.cpp (9,232 bytes).

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Last changed 08/01/02.