DD /dev/zero to /dev/null fun!

[Rich43]

This command is cool.. it gets a bunch of zeros from /dev/zero and discards them to /dev/null...

dd if=/dev/zero of=/dev/null bs=900000
1647696600000 bytes (1.6 TB) copied, 125.442 s, 13.1 GB/s

I get 13GB/s!!

 

[memyselfandi]

hmmm ... what's that on as it's not that quick ... on my C2D 2180 based server I get the following:

belgarath:~ # dd if=/dev/zero of=/dev/null bs=900000
3300703+0 records in
3300702+0 records out
2970631800000 bytes (3.0 TB) copied, 133.523 s, 22.2 GB/s

and I suspect others can get a lot faster than that ...

 

[thegoonden]

Just don't fumble it and type /dev/ram or /dev/hdsomething


41.5GB/s

 

[Swanster]

This is a very poor test of performance; I just got 44.2 GB/s on a Sempron 2500

 

[BillytheImpaler]

This is a very poor test of performance; I just got 44.2 GB/s on a Sempron 2500

Hmm, any idea why I'm only getting 1.3 GB/s on my X2 3800+? It's got a single 1 GiB stick of DDR2-533.

EDIT: For comparison's sake my dual 1 GHz G4 PowerMac gets 1.1 GB/s. (3x 512 MiB PC133) :/

 

[Deanje]

Hmm, any idea why I'm only getting 1.3 GB/s on my X2 3800+? It's got a single 1 GiB stick of DDR2-533.

EDIT: For comparison's sake my dual 1 GHz G4 PowerMac gets 1.1 GB/s. (3x 512 MiB PC133) :/

I only got 1.3GB/s on my 2 x 2GHz G5 Powermac with 3GB of RAM

 

[Swanster]

Hmm, any idea why I'm only getting 1.3 GB/s on my X2 3800+? It's got a single 1 GiB stick of DDR2-533.

EDIT: For comparison's sake my dual 1 GHz G4 PowerMac gets 1.1 GB/s. (3x 512 MiB PC133) :/

I honestly have no idea. Maybe only certain drivers are optimised for copying nothing to nowhere?....

 

[thegoonden]

Could be a realtime clock setting just.

It really is a silly test, as my 1.6 cellyM lapper scores the exact same as the AMD box in me sig.

 

[whitecrook]

What really counts is the BogoMips!!!!eleventy

 

[thegoonden]

I love the idea of bogomips.

"all mips measures are bogus, therefor, we'll measure how many times the cpu can do crap all in a second, and it'll be uber bogus, but of a standard level of bogosity, useless in absolutes, vital in comparison"
Roughly speaking.

 

[BillytheImpaler]

A 2.0 GHz Core 2 Duo iMac with 1 GiB DDR2 667 (dual channel) gets me 3.6 GB/s.

 

[Dj_Jestar]

john@john ~ $ dd if=/dev/zero of=/dev/null bs=900000
146806235+0 records in
146806234+0 records out
132125610600000 bytes (132 TB) copied, 6822.07 s, 19.4 GB/s

 

[ChrisB]

PPC MiniMac (Debian)

chrisb@basil:~$ dd if=/dev/zero of=/dev/null bs=900000
17425247+0 records in
17425246+0 records out
15682721400000 bytes (16 TB) copied, 556.307 seconds, 28.2 GB/s

 

[Rich43]

john@john ~ $ dd if=/dev/zero of=/dev/null bs=900000
146806235+0 records in
146806234+0 records out
132125610600000 bytes (132 TB) copied, 6822.07 s, 19.4 GB/s

You left it going for ages haha...

I tried it on my websites server and I got:

root@nonobloodyno:~# dd if=/dev/zero of=/dev/null bs=900000
330224+0 records in
330223+0 records out
297200700000 bytes (297 GB) copied, 25.2935 s, 11.8 GB/s

root@nonobloodyno:~#

Swanster appears to be winning so far...

 

[thegoonden]

Isn't it funny though, how all the little proggies that form the core of Linux, like cat and top and ps and dd and all those things, can provide so much endless entertainment.

I must think of new things to do with cat every other day (that's ConCATinate, as opposed to a member of the family Felus).
And the really odd bit is, that you'd not necessarily find them, or find out their abilities in normal modern day-to-day Linux use. These days you'll only know much about them if you've read a book or just happen to be an oldschool *nix dude, who actually used it for real work once.


example of dd........
Don't want to pay ££££ for Acronis trueimage?

(to backup a windows C:\ to a backups partition mounted in Linux.

dd if=/dev/hda1 | gzip > /mnt/backups/saveass.img.gz

to restore.......

gunzip /mnt/backups/saveass.img.gz | dd of=/dev/hda1

( you can do the same exact thing with cat as well)