# Benchmarking/Data storage devices

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This article covers several Linux-native apps that benchmark I/O devices such as HDDs, SSDs, USB thumb drives, etc. There is also a "database" section specific to SSDs meant to capture user-entered benchmark results.

## Overview

Several I/O benchmark options exist under Linux.

- Using hdparm with the -Tt switch, one can time sequential reads. This method is independent of partition alignment!
- There is a graphical benchmark called gnome-disks contained in the gnome-disk-utility package that will give min/max/ave reads along with ave access time and a nice graphical display. This method is independent of partition alignment!
- The dd utility can be used to measure both reads and writes. This method is dependent on partition alignment! In other words, if you failed to properly align your partitions, this fact will be seen here since you are writing and reading to a mounted filesystem.
- Bonnie++ (caution: by default, bonnie++ write at least twice the RAM size on disk. If you want to preserve your SSD, use non default option)

## Using hdparm

    # hdparm -Tt /dev/sdX
    /dev/sdX:
    Timing cached reads:   x MB in  y seconds = z MB/sec
    Timing buffered disk reads:  x MB in  y seconds = z MB/sec

Note: One should run the above command 4-5 times and manually average the results for an accurate evaluation of read speed per the hdparm man page.

## Using gnome-disks

    # gnome-disks

Users will need to navigate through the GUI to the benchmark button ("More actions..." => "Benchmark Volume..."). Example

## Using systemd-analyze

    systemd-analyze plot > boot.svg

Will plot a detailed graphic with the boot sequence: kernel time, userspace time, time taken by each service. Example

## Using dd

Note: This method requires the command to be executed from a mounted partition on the device of interest!

First, enter a directory on the SSD with at least 1.1 GB of free space (and one that obviously gives your user wrx permissions) and write a test file to measure write speeds and to give the device something to read:

    $ cd /path/to/SSD
    $ dd if=/dev/zero of=tempfile bs=1M count=1024 conv=fdatasync,notrunc status=progress
    1024+0 records in
    1024+0 records out
    w bytes (x GB) copied, y s, z MB/s

Tip: See dd-benchmark for an explanation on the requirement to `sync` and further related `dd` options.

Next, clear the buffer-cache to accurately measure read speeds directly from the device:

    # echo 3 > /proc/sys/vm/drop_caches
    $ dd if=tempfile of=/dev/null bs=1M count=1024 status=progress
    1024+0 records in
    1024+0 records out
    w bytes (x GB) copied, y s, z MB/s

Now that the last file is in the buffer, repeat the command to see the speed of the buffer-cache:

    $ dd if=tempfile of=/dev/null bs=1M count=1024 status=progress
    1024+0 records in
    1024+0 records out
    w bytes (x GB) copied, y s, z GB/s

Note: One should run the above command 4-5 times and manually average the results for an accurate evaluation of the buffer read speed.

Finally, delete the temp file

    $ rm tempfile

Note: Some SSD controllers have compression hardware, which may skew benchmark results. See http://www.pugetsystems.com/labs/articles/SSDs-Advertised-vs-Actual-Performance-179/

See also Core utilities#dd.

## Using dcfldd

Dcfldd doesn't print the average speed in MB/s like good old dd does but with time you can work around that.

Time the run clearing the disk:

    # time dcfldd if=/dev/zero of=/dev/sdX bs=4M
    18944 blocks (75776Mb) written.dcfldd:: No space left of device
    real     16m17.033s
    user     0m0.377s
    sys      0m51.160s

Calculate MB/s by dividing the output of the dcfldd command by the time in seconds. For this example: 75776Mb / (16.4 min * 60) = 77.0 MB/s.

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