Test network speed without wasting disk

dd if=/dev/zero bs=4096 count=1048576 | ssh user@host.tld 'cat > /dev/null'
The above command will send 4GB of data from one host to the next over the network, without consuming any unnecessary disk on either the client nor the host. This is a quick and dirty way to benchmark network speed without wasting any time or disk space. Of course, change the byte size and count as necessary. This command also doesn't rely on any extra 3rd party utilities, as dd, ssh, cat, /dev/zero and /dev/null are installed on all major Unix-like operating systems.
Sample Output
user@host.tld's password:
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB) copied, 171.841 seconds, 25.0 MB/s

6
By: atoponce
2010-06-08 18:49:51

What Others Think

This will compress really well with ssh (/dev/zero is the same byte over and over). For a better test replace /dev/zero with /dev/urandom,
sdadh01 · 660 weeks and 2 days ago
The SSH connection is adding overhead with encryption, thus the reason to use /dev/zero to level the playing field, otherwise, your bandwidth will be considerably less.
atoponce · 660 weeks and 2 days ago
Or you could use netcat and use /dev/urandom. This way you don't have the overhead of compression and use a more realistic approach to test your network. dd if=/dev/urandom bs=4096 count=1048576 | nc host.tld 1234 and on host.tld you should start netcat with the 'listen' parameter nc -l -p 1234 | dd of=/dev/null Actually, if you really wanna test your network you should go the iperf or netperf way (and use UDP or TCP, depending on how you wanna test it).
paragao · 660 weeks and 1 day ago
Right. This isn't meant to be an accurate network bandwidth benchmarking tool. This is useful for nothing more than a rough estimate, and it doesn't rely on any external 3rd party tool, and it's cross platform, which was the goal.
atoponce · 660 weeks and 1 day ago
this command is helpful for a 'rough estimation' but i would add the ssh '-c arcfour' option.
cp · 656 weeks and 4 days ago
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Perfecthomepugs · 13 weeks and 4 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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