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I'm doing a sudo dd if=/dev/urandom of=/dev/sdc bs=4096 The disk is 3Tb. It's been 14 hours it's running, is it an acceptable timeframe, when can I expect it to finish ? Can I calculate an expected time to process that operation ?

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According to http://pc.net/helpcenter/answers/seven_pass_erase_duration it would take around 16 hours... (250 gig single overwrite in around 79 minutes).

It depends on your Computers speed to create random seed from /dev/urandom, your device speed, your port speed.

btw using /dev/urandom is not more secure then using /dev/zero, which is also faster:

root@m2310:~# dd if=/dev/zero of=file.txt count=1024 bs=1024
1024+0 records in
1024+0 records out
1048576 bytes (1.0 MB) copied, 0.00741118 s, 141 MB/s
root@m2310:~# dd if=/dev/urandom of=file.txt count=1024 bs=1024
1024+0 records in
1024+0 records out
1048576 bytes (1.0 MB) copied, 0.165744 s, 6.3 MB/s

Reads with 141 MB/s from /dev/zero and 6.4 MB/s from /dev/urandom

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  • and /dev/zero is faster I bet ? – euri10 Mar 11 '16 at 8:37
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    it is... a test machine read 141 mb/s from /dev/zero and 6.3mb/s from /dev/urandom – hexathos Mar 11 '16 at 8:40
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    @euri10 use shred of coreutils: man7.org/linux/man-pages/man1/shred.1.html ; it can be used on block devices (e.g. shred -v -n 1 /dev/sdc, shred -v -n 0 -z /dev/sdc) – Tom Yan Mar 11 '16 at 10:04
  • @TomYan any idea of the time it takes ? – euri10 Mar 11 '16 at 12:22
  • @euri10 depends on the sequential write speed of your HDD. with shred the random data generation would not be the bottleneck. – Tom Yan Mar 11 '16 at 14:47

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