Use "dd" Command to Test I/O Speed

Linux Tutorials - Herong's Tutorial Examples

∟Use "dd" Command to Test I/O Speed

This section provides a tutorial example on how to test I/O speed of hard disk and USB drives using the 'dd' command with different block sizes.

The "dd (data duplicator)" command can also be used to measure I/O (Input/Output) speed of a given storage device.

Tests on my CentOS 8.0 computer

1. Test input (writing) speed of the internal hard disk. I see that bigger block size (bs) is more efficient when writing to the hard disk.

herong$ pwd
/home/herong

herong$ dd if=/dev/zero of=one-giga bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.255833 s, 4.2 GB/s

herong$ dd if=/dev/zero of=one-giga bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.98674 s, 540 MB/s

herong$ ls -l one*
-rw-rw-r--. 1 herong herong 1073741824 Apr  5 03:23 one-giga

2. Test output (reading) speed of the internal hard disk. I see that bigger block size (bs) is more efficient when reading from the hard disk. I also see that reading is two times slower than writing, which is a little surprise to me.

herong$ dd if=one-giga of=/dev/null bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.113039 s, 9.5 GB/s

herong$ dd if=one-giga of=/dev/null bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.18922 s, 903 MB/s

3. Test input (writing) speed of a USB drive. I see that the input speed on USB drive is about the same as the hard disk with block size of 1 KB, which is a little surprise to me.

(USB drive is mounted on /media)
herong$ df /dev/sdc1
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sdc1        7813124 1146116   6667008  15% /media

herong$ cd /media

herong$ sudo dd if=/dev/zero of=one-giga bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.937841 s, 1.1 GB/s

herong$ sudo dd if=/dev/zero of=one-giga bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 2.12935 s, 504 MB/s

4. Test output (reading) speed of the same USB drive. I see that the output speed on USB drive is about the same as the hard disk for both large and small block sizes, which is a little surprise to me.

herong$ dd if=one-giga of=/dev/null bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.115699 s, 9.3 GB/s

herong$ dd if=one-giga of=/dev/null bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.13126 s, 949 MB/s

Tests on my macOS 10 computer

1. Test input (writing) speed of the internal hard disk. I see that the input speed of my macOS hard disk is much slower that my CentOS computer.

herong$ pwd
/Users/herong

herong$ dd if=/dev/zero of=one-giga bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes transferred in 0.741450 secs (1,448,164,705 bytes/sec)

herong$ dd if=/dev/zero of=one-giga bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 4.046084 secs (265,378,040 bytes/sec)

2. Test output (reading) speed of the internal hard disk. I see that the output speed is much faster than input speed, which makes sense.

herong$ dd if=one-giga of=/dev/null bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes transferred in 0.218341 secs (4,917,726,275 bytes/sec)

herong$ dd if=one-giga of=/dev/null bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 2.320591 secs (462,701,888 bytes/sec)

3. Test input (writing) speed of the same USB drive. I see that the input speed on the same USB drive on macOS is about 200 times slower than than CentOS. I think the main cause of the speed drop is the USB to USB-C cable used to connect the USB drive.

(USB drive is auto mounted on /Volumes/NO NAME)
herong$ df
Filesystem    512-blocks      Used Available Capacity Mounted on
...
/dev/disk3s1    15626248   2294808  13331440    15%   /Volumes/NO NAME

herong$ cd '/Volumes/NO NAME'

herong$ sudo dd if=/dev/zero of=one-giga bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes transferred in 214.298787 secs (5,010,490 bytes/sec)

herong$ sudo dd if=/dev/zero of=one-giga bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 208.157021 secs (5,158,326 bytes/sec)

4. Test output (reading) speed of the same USB drive. I see that the output speed on USB drive is about 600 times faster than the input speed, which is a big surprise to me.

herong$ dd if=one-giga of=/dev/null bs=64k count=16k
16384+0 records in
16384+0 records out
1073741824 bytes transferred in 0.353298 secs (3,039,196,314 bytes/sec)

herong$ dd if=one-giga of=/dev/null bs=1k count=1024k
1048576+0 records in
1048576+0 records out
1073741824 bytes transferred in 2.318289 secs (463,161,373 bytes/sec)