Why is the Time Machine Back-up encryption taking so long?

My Seagate backup drive takes many hours to back up because of this fault. I contacted Seagate and they said "Unfortunately we do not support drive encryption with the Expansion drive." What external backup drives do support encryption? It seems pointless to have a password-protected computer and not protect your backup, which has the same material on it!

Although this is now a three-year-old thread, I found this advice very useful, even on macOS Sierra. I was trying to do an encrypted Time Machine backup to a 2 TB external USB drive, fresh out of the box (and apparently not encrypted from the get-go), from a MacBook Pro 13" 2016 model. The Time Machine backup itself (about 200 GB) took maybe three hours... but as for the encryption, even after half a day the display still showed only 10% finished. I was wondering whether I really needed to let the computer grind away at encryption for a full week!

I took your advice and stopped the backup, reformatted the external drive in Disk Utility as encrypted, and then reassigned the disk as a Time Machine backup. The backup and encryption took perhaps three hours tops!

All I can assume is that formatting the disk first as encrypted using Disk Utility and then doing the Time Machine backup saved the step of macOS actually encrypting every single byte on an already-formatted hard disk, even though the lion's share of that hard disk was empty. Format and encrypt first, then do the backup... that seems the most efficient way, it appears.

Thanks again for the great tip!

Jeff

Worked for me! Thanks Matthew! I was backing to a 4TB Seagate drive and had checked on the encrypt backup option in time machine. I happen to have already had the drive for aged to Mac OS Extended Journaled and encrypted. Time machine was stuck at like 3% "encrypting". I ejected the drive, even though it said it was encrypting. Removed the drive as a backup disk from Time Machine settings. Plugged it back in, set the drive as a time machine backup, this time with encrypt backups not checked. A fresh back started and did not need to do a complete backup all over, it was just the next incremental backup.

I also had the same problem and Matthew's answer worked for me.

However, another solution I discovered was that if I used macOS Server to set up the disk as a network backup, the encryption and backup process went just as fast as Matthew's method and resulted in an encrypted disk image on an unencrypted volume. Across ethernet, it was about 2.5 hours for 250 GB, so I'm going to try it on the same machine and see if it's any faster (I doubt it will be, as processing and disk speeds seem to be the limiting factors).

Server is only $20 and you can do lots with it (including setting up an internet contacts/calendar server if you don't want to use Google or iCloud).

From my observations Lion is encrypting every byte on the drive--whether or not it's in use. On the USB 2 Western Digital Passport drive I'm currently encrypting it's working at about 35 Gigs/hour—so > 24 hours for a terrabyte.

Given the other drive I use is showing faults under Lion I haven't actually completed this process, but I fully expect subsequent backups to be speedy once the initial encryption is finished.

Aso see #31 in Time Machine - Frequently Asked Questions.

Yup, if it's actually progressing just leave it. CoreStorage is meant to be resiliant about encryption, so you could *probably* sleep your Mac or eject the drive before it's finished, but I wouldn't :-) CS seems quite happy about Time Machine interrupting it every hour for the latest backup.

You can see more detailed progress at the command line by typing the following and looking for 'Size (Total)' and 'Size (Converted)':

diskutil cs list

I recently upgraded my hard drive after moving to Lion and decided to just start a new Time Machine backup from scratch to avoid headaches using a 1 TB WD My Book for Mac, connected through USB. I too am doing an encrypted Time Machine backup, and realized that the encryption will not be done before I have to take my laptop somewhere. So - I took a chance (since I'm starting from scratch anyway) and tested whether encryption would continue after shutting down the laptop. It did -- continuing to encrypt after shutting down the laptop, restarting, and reconnecting the Time Machine disk (at a snail's pace, but it's a large drive).

Probably no help to you now, but to others in the future -- it will continue to encrypt if you have to disconnect your Time Machine disk during encryption. Seems like at this rate the disk will be encrypted in a week -- but oh well. Done in the background with no interruption to what I'm doing!

I am having the same problem on Maverick 10.9.1. Did you find any resolution? The encryption for my backup has been running for 2 days and is still only at 50%.

On maverics as well... Have two seperate backup drives, one is 2.5 usb3 drive and it backups in less than a few hours. Other drive is a 3.5 green drive with usb 2 connection, i would expect it to be slower, but its 1000x slower, its at 64%, its been DAYS. Decided to remove the 3.5 drive as a time machine drive, and also deleted the time machine backup folder from it, but it continues encrypting. Even after unplugging it and plugging it back in it persists

I found 24 hours to be way too long to wait, so I tried the following and it worked for me.

TurnTime Machine off. Open Disk Utility and selected the drive you want to back up to, and go to the erase tab. Click on the drop down menu and select "Mac OS Extended (Journaled, Encrypted)", enter the password you want and contine. In a few seconds it should have an empty drive for you, encryped. You then tell Time Machine to use this drive for backups, and after a few seconds to a minute of "Prearing Backup" it will just start copying the files for you. This way your backup is encryped without the long wait.

I hope this helps for you too.

I'm on day 5 of my first Mac - having spent three hours watching my encryption seemingly moving at snails space and a backup indicating several hours of only 32GB of data I decided to look for help.

Thank you for your advice - only 13 minutes to go (5 having passed) since the disc was erased and encrypted!!

Much appreciated.

Thank you very much to take the effort to post your invaluable TIP

Great, fantastic.! 🙂

My iMac (Bought in December 3013) and me are so happy!