Test your total disk IO capacity, regardless of caching, to find out how fast the TRUE speed of your disks are

time (dd if=/dev/zero of=blah.out bs=256M count=1 ; sync )
Depending on the speed of you system, amount of RAM, and amount of free disk space, you can find out practically how fast your disks really are. When it completes, take the number of MB copied, and divide by the line showing the "real" number of seconds. In the sample output, the cached value shows a write speed of 178MB/s, which is unrealistic, while the calculated value using the output and the number of seconds shows it to be more like 35MB/s, which is feasible.
Sample Output
1+0 records in
1+0 records out
268435456 bytes (268 MB) copied, 1.50648 seconds, 178 MB/s

real    0m7.119s
user    0m0.002s
sys     0m0.649s

2
By: tkunz
2009-07-14 20:19:23

1 Alternatives + Submit Alt

What Others Think

nice but.. to play the real game use www.iozone.org or bonnie
ioggstream · 483 weeks ago
What you're doing here is really testing *filesystem* performance rather than disk IO. For actual "disk IO", do what ioggstream said or use hdparm: hdparm -t /dev/sda this will test drive throughput by actually streaming a write off the disk. Use the -T option to test how fast the cpu, memory, & linux disk buffer cache can theoretically go. The underlying filesystem can
bwoodacre · 483 weeks ago
you need to also sync before time command to make sure that the previous file system writes are synched before you start the test: sync; time { dd if=/dev/zero of=test bs=256m count=1; sync; }
bluejay · 143 weeks 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?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands



Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: