Disk Speed Test (Read/Write): HDD, SSD Performance in Linux

From this article you’ll learn how to measure an input/output performance of a file system on such devices as HDD, SSD, USB Flash Drive etc.

I’ll show how to test the read/write speed of a disk from the Linux command line using dd command.

I’ll also show how to install and use hdparm utility for measuring read speed of a disk on Linux Mint, Ubuntu, Debian, CentOS, RHEL.

To get the accurate read/write speed, you should repeat the below tests several times (usually 3-5) and take the average result.

Cool Tip: How to choose SSD with the best quality/price relation! Read more →

dd: TEST Disk WRITE Speed

Run the following command to test the WRITE speed of a disk:

$ sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 3.28696 s, 327 MB/s

dd: TEST Disk READ Speed

The file tempfile, that has just been created by the previous command, was cached in a buffer and its read speed is much higher then the real read speed directly from the disk.

To get the real speed, we have to clear cache.

Run the following command to find out the READ speed from buffer:

$ dd if=tempfile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 0.159273 s, 6.7 GB/s

Clear the cache and accurately measure the real READ speed directly from the disk:

$ sudo /sbin/sysctl -w vm.drop_caches=3
vm.drop_caches = 3
$ dd if=tempfile of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 2.27431 s, 472 MB/s

dd: TEST Read/Write Speed of an External Drive

Cool Tip: Have added a new drive to /etc/fstab? No need to reboot! Mount it with one command! Read more →

To check the performance of some External HDD, SSD, USB Flash Drive or any other removable device or remote file-system, simply access the mount point and repeat the above commands.

Or you can replace tempfile with the path to your mount point e.g.:

$ sync; dd if=/dev/zero of=/media/user/MyUSB/tempfile bs=1M count=1024; sync

Reminder: All the above commands use the temporary file tempfile. Don’t forget to delete it when you complete the tests.

hdparm: Test HDD, SSD, USB Flash Drive’s Performance

hdparm is a Linux command line utility that allows to set and view hardware parameters of hard disk drives.

And it can also be used as a simple benchmarking tool that allows to quickly find out the READ speed of a disk.

hdparm is available from standard repositories on the most Linux distributions.

Install hdparm depending on your Linux distribution.

Cool Tip: Troubleshooting an issue with a hard drive performance? It will be a good idea also to test download/upload Internet speed. It can be easily done from the Linux command line! Read more →

On Linux Mint, Ubuntu, Debian:

$ sudo apt-get install hdparm

On CentOS, RHEL:

$ sudo yum install hdparm

Run hdparm as follows, to measure the READ speed of a storage drive device /dev/sda:

$ sudo hdparm -Tt /dev/sda
/dev/sda:
 Timing cached reads:   16924 MB in  2.00 seconds = 8469.95 MB/sec
 Timing buffered disk reads: 1386 MB in  3.00 seconds = 461.50 MB/sec

10 Replies to “Disk Speed Test (Read/Write): HDD, SSD Performance in Linux”

  1. I think you missed the best software package for this kind of tests. It’s called fio:
    https://github.com/axboe/fio/

  2. How to check sdb drive?
    Should I use /dev/sdb instead of /dev/zero here:
    sync; dd if=/dev/zero of=/media/user/MyUSB/tempfile bs=1M count=1024; sync
    ?

  3. @JON

    > bs=4k and count=256k
    k means what it always means: about 1,000, but in the case of computers (here), usually 1024. “bs” means block size, “count” means number of blocks. So this means write 4k x 256k bytes. 1k x 1k = 1 megabyte (about 1,000 x about 1,000 = about 1,000,000). How many megabytes? Since we already took care of the ‘k’s; 4x 256 = 1024 (aka about 1000, or 1k again.) What’s 1k x 1k x 1k? 1 gigabyte (about 1,000,000,000.) You wrote 1 gigabyte of zeros.

    Therefore,

    > bs=1M and count=256k

    1M = (1k x 1k)
    (1k x 1k) x 1k(the k from “count”) = 1 gigabyte
    1 gigabyte x 256 = 256 gigabytes.

    You were writing 256 gigabytes of zeros. Your drive is only 150 gigabytes in size. It won’t hurt your drive, it will just delete everything on your drive. When it fills your drive, it will stop.

    The “if” is not from ram, it is a program (/dev/zero) in your system disguised as a file but whenever it is read is just endless zeros.

  4. I must have done something wrong. I tested first with bs=4k and count=256k.
    It finished quickly.
    Afterwards I decided myself to alter the parameters like so: bs=1M and count=256k
    I didn’t know exactly what I was doing. I left it running not having slightest hunch if it’s wrong to interrupt it via Ctrl-C. It run approximately 1000 seconds having written almost 100GB of all 150GB free on the SSD. Only then I’ve read the man pages searching for clues but still didn’t found. So I have a couple of questions if kindly allowed. That ‘k’ at the end of count I am not sure of it’s meaning or even if it makes sense. I have to also ask what would have happened if the command filled the whole free space? Would it have stopped by itself with message/error? Was it dangereous for an ssd doing this. The fact I performed it from sysresccd on ssd with Windows installed has any effect on outcome?
    I mean the if = is it from the RAM memory? I specified an of= on the ssd after mounting it like /mnt/windows/some.output.file. Is the way I did it significant for the results?

  5. “Reminder: All the above commands use the temporary file tempfile. Don’t forget to delete it when you complete the tests.”
    I can not find any place where you instruct as to how to delete the tempfile. How is this done safely?

  6. Anyone has hdparm version for Android?

  7. soooooooooo simple!!!!!…….

  8. Good Information!

  9. Awesome. Thanks.

    williamj@SilverK:~$ sync; dd if=/dev/zero of=tempfile bs=1M count=1024; sync
    1024+0 records in
    1024+0 records out
    1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.313688 s, 3.4 GB/s
    williamj@SilverK:~$ dd if=tempfile of=/dev/null bs=1M count=1024
    1024+0 records in
    1024+0 records out
    1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.093416 s, 11.5 GB/s
    williamj@SilverK:~$ sudo /sbin/sysctl -w vm.drop_caches=3
    [sudo] password for williamj: 
    vm.drop_caches = 3
    williamj@SilverK:~$ dd if=tempfile of=/dev/null bs=1M count=1024
    1024+0 records in
    1024+0 records out
    1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.7639 s, 1.4 GB/s

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