I have a brand new hard drive with nothing on it. I also bought a brand new external hard drive to use with my MacBook Pro. I'm in the process of backing up to time machine and the encryption is taking forever. Why is it taking so long when there's nothing on my hard drive?

2 Answers 2


The amount of time it takes to encrypt a drive is a function of its size, not its contents.

Your brand-new hard drive full of zeroes still needs to be scrambled so that no one can figure out that it’s full of zeroes. That will take just as long as encrypting the same amount of arbitrary values.

  • but why do we need to do that? I don't mind that an attacker can discover than half my hard disk is un-used, as long as he cannot read the used part
    – Ant
    Mar 19, 2018 at 17:35
  • Same question, if you select a pre-encrypted disk it won't do that. What's the difference?
    – rinat.io
    Sep 1, 2019 at 15:29

if you don't want your whole hard drive encrypted you can partition it (splits your drive into another segment of the size you wish) and then just backup to that. This will limit backup size though.

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