FileVault disk encryption very slow

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Level 1

4 points

FileVault disk encryption very slow

Running Mojave 10.14.2 on a MacBook (Retina, 12-inch, 2017) . I have created an unencrypted bootable backup via Carbon Copy Cloner. I then booted into my backup and enabled encryption.

Now I have booted my internal drive and am watching the status of the encryption. It is very slow overall, and only seems to get decent throughput while I am actively at the computer. I am using Amphetamine to keep the computer awake and monitoring via Activity Monitor.

When actively typing or mousing, I see the disk activity at between 20 and 30 MB/sec. If I leave the computer for a while, I see the disk activity go down to a few KB/sec. Amphetamine is still keeping the computer awake.

Any idea why it is so slow?

Posted on Jan 19, 2019 4:53 PM

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Answer 1

John Galt

Level 10

156,596 points

Jan 19, 2019 8:22 PM in response to PaulWaldo

It's slow because it takes time to encrypt terabytes of data. One terabyte is one million million bytes. That's a lot.

FileVault is designed to work in the background; as you probably observed encryption does not have much effect on anything else you're doing. It could be designed to work faster and finish sooner, but then people would complain their Macs are slow and their batteries are draining and AppleCare would get a lot of phone calls.

I have created an unencrypted bootable backup via Carbon Copy Cloner. I then booted into my backup and enabled encryption.

SSD or hard disk drive? HDD will take a few days.

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Answer 2

John Galt

Level 10

156,596 points

Jan 20, 2019 7:14 AM in response to PaulWaldo

It'll finish in three or four days.

I am using Amphetamine to keep the computer awake and monitoring via Activity Monitor.

You know you can just set Energy Saver to "never sleep". Or use the caffeinate command. Or just play iTunes. Or do a lot of other things. It probably wouldn't surprise you that a lot of "My Mac won't sleep!!!" questions on this site are from users who installed some clever hack and then forgot about it.

Make sure that disk isn't sleeping. Some hard disk manufacturers have sleep behavior coded in firmware that can't be changed.

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Answer 3

PaulWaldo Author

Level 1

4 points

Jan 20, 2019 5:02 AM in response to John Galt

Thanks for the reply, John Galt. The disk is a 1 TB spinning platter hard drive connected via USB 3.

I understand and appreciate that the conversion should be throttled while the computer is not in use. Unfortunately, I see the opposite (according to Activity Monitor). The idle computer shows about 2 KB/sec disk activity. As soon as I press a key, the disk activity shoots up to about 30 MB/sec. I would expect that the idle speed would be high and it would drop when I am active on the computer.

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FileVault disk encryption very slow

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