/dev/urandom, how long does it take on 500gb?

StaticPhilly · 2011-01-24 10:14:01

hello all,

just wondering if anyone could give me a ruff time urandom takes to completely randomize a 500gb hdd?

i started it 17 hours ago and its still going, starting to get sick of waiting

cheers,
phil

eldragon · 2011-01-24 10:38:54

who are you giving this hdd to that you are this worried about your family pics?

how are you piping urandom to the hdd?

karol · 2011-01-24 10:55:30

eldragon wrote:

how are you piping urandom to the hdd?

If OP is using very small chunks then it will take very long.

StaticPhilly, can you post the exact command you used? I guess you should have done a small scale test to see how long it will take to overwrite e.g. 1 GB.
The speed can be < 1MB/second.

EDIT: Not sure if it makes sense, but

karol@black ~]$ time sudo < /dev/urandom dd bs=1 count=10000000 >/dev/null
10000000+0 records in
10000000+0 records out
10000000 bytes (10 MB) copied, 49,2306 s, 203 kB/s

real    0m49.240s
user    0m2.613s
sys    0m44.954s

Last edited by karol (2011-01-24 11:00:43)

StaticPhilly · 2011-01-24 11:05:29

the command i ran was

dd if=/dev/urandom of=/dev/sda bs=1M

dont really want to interupt it, otherwise i probally would test it

cheers,
phil

karol · 2011-01-24 11:33:18

It shouldn't take more than 50hrs :-)

StaticPhilly · 2011-01-24 11:38:25

hahaha, guess ill just have to hide the laptop thats running it so i dont keep checking every 5 mins

thanks

IncredibleLaser · 2011-01-24 11:58:21

Here's how I wipe my HDDs:

Partition the drive so that it's only one big partition (say /dev/sdd1)
encrypt the partition with a random password
mount it (e.g. to /dev/mapper/wipeme)
dd if=/dev/zero of=/dev/mapper/wipeme $YOUROPTIONSHERE
unmount

If you are super-paranoid, you can overwrite the partition table and the luks header with /dev/urandom. But let's be honest, it would have been sufficient to just overwrite your harddisks with zeroes (dd if=/dev /zero of=/dev/sdd or whatever) in the first place. See this german article for more info. It claims that the probability to restore only one byte after a hard disk has been overwritten with zeroes once is about 0.97 percent - if you know the exact position of every bit.

karol · 2011-01-26 17:15:46

Are we there yet?

keenerd · 2011-01-26 19:38:45

Urandom is kind of slow. Not as slow as random, but still really slow. If you are going to make gigabytes of data, use frandom instead.

Here is a quick benchmark on my slow netbook -
random: 8 B/s
urandom: 740 kB/s
frandom: 30 MB/s

Frandom is 40 times faster! I would expect it to do about 150 MB/s on a desktop. For your drive, around an hour altogether.

Edit: To see the progress on your dd, send it a USR1 signal. Read "man dd" for an example.

Last edited by keenerd (2011-01-26 19:44:16)

Arch Linux

#1 2011-01-24 10:14:01

/dev/urandom, how long does it take on 500gb?

#2 2011-01-24 10:38:54

Re: /dev/urandom, how long does it take on 500gb?

#3 2011-01-24 10:55:30

Re: /dev/urandom, how long does it take on 500gb?

#4 2011-01-24 11:05:29

Re: /dev/urandom, how long does it take on 500gb?

#5 2011-01-24 11:33:18

Re: /dev/urandom, how long does it take on 500gb?

#6 2011-01-24 11:38:25

Re: /dev/urandom, how long does it take on 500gb?

#7 2011-01-24 11:58:21

Re: /dev/urandom, how long does it take on 500gb?

#8 2011-01-26 17:15:46

Re: /dev/urandom, how long does it take on 500gb?

#9 2011-01-26 19:38:45

Re: /dev/urandom, how long does it take on 500gb?

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