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Pavel Tankov
Asked: 2018-03-03 03:00:01 +0800 CST

Is it faster to wipe out multiple hard disks with dd=/dev/zero simultaneously?

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I have 3 hard disks 1T each. I want to wipe them out completely. I decided yo use dd like so:

dd if=/dev/zero of=/dev/sdb bs=1M
dd if=/dev/zero of=/dev/sdc bs=1M
dd if=/dev/zero of=/dev/sdd bs=1M

Since it takes a while for the commands to complete, can I assume that it will be faster if I open 3 different consoles and execute the commands simultaneously?

Will it be 3 times faster compared to executing them sequentially?

hard-drive

1 Answers

  1. Best Answer

    OK, I went on and did a small experiment. It seems that running the commands simultaneously isn't exactly 3 times faster, but it's way faster than one-by-one.

    I ran them all, then monitored the progress by typing:

    watch -n5 'sudo kill -USR1 $(pgrep ^dd)'

    When all 3 commands are running, I get about 100 MB/s. If I stop 2 other and leave just 1 instance of dd running, the speed increases to about 120 MB/s.

    That is of course just in the beginning while the disk is being written on the outer-most cylinders, where it's fastest. Later speed drops proportionally a little bit, but still the conclusion is this:

    Yes, it is a lot faster to do this wiping out simultaneously.

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