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

Definitely helped! First attempt at encrypted TM backup, using Seagate 3TB Backup Plus. Got stuck in the (apparent) 2 day whole drive encryption before starting to do the actual backup. Killed that as you suggested and erased it. Started again with Disk Utility, done encrypting in seconds. I added another partition (2 were allowed), this one unencrypted for general storage, media serving, etc. (Not sure if I could have also accomplished this in my setup with an encrypted partition but I had the space and it looks like I can merge it back later into the encrypted partition if desired.) Now doing the initial encrypted TM backup of 300GB, looks like it will take about 3 hours total (getting data transfer rates between 25 and 150MB/sec on USB 3.0). Once that's done, I plan to plug the drive into my Airport Extreme and do the incremental backups over Wifi.

Hi Matthew

thanks sooooooo much for this, you have saved me loads of time!

your fix works really well, i.e. encrypting the back up disc before backing up with Time Machine instead of after.

After I'd done this my first back up took less than 45mins 🙂

Thank you so so much for taking the trouble to post your answer 🙂

Angie Bongos

(NB in case relevant for anyone I used this with WD My Passport for Mac.)

ALSO in case useful to anyone...

I started DEcrypting my previously-encrypted back up disc by mistake and it was taking aaaaaaages, and I could not find any way to cancel it. The only thing that worked was doing the same as Matthew advised for stopping an encryption process,

i.e. if anyone's stuck in a lengthy encryption or decryption process, then Matthew's fix will work!

Top tip for other mac newbies from me....

I didn't know where to find Disc Utilities!!
If you are likewise confused, here are simple instructions:

Click on Finder - look for Devices - click on MacBook (in my case)

Click on Applications

Click on Utilities
Click on Disc Utility

Click on the icon (picture of a hard-drive and stethoscope in my case)

That will open disc utility and you can then follow Matthew's instructions

Cheers 🙂

One detail in this procedure is left out. And that is after you encrypt the drive using disk utility, are you supposed to enable or disable encryption inside Time Machine?

ah glad you asked this erotavlas/ Salvatore 🙂

🙂 ANSWER - leave the box ticked (I think or unticked but either way) in order to ENABLE encryption in Time Machine, even though you've already encrypted the whole/partitionof the drive in Disc Utility with the process outlined in Matthew's reply.

Cheers from AngieBongos

PS I did not know either...! so I guessed!

here's more detail for anyone that needs convincing or is stuck with it all as I was!

😟 the way NOT to do it! 😟

what I did (which is what you don't want to do!) was to tick or untick (can't remember which way round it is) the box re encryption in order to DISable encryption in Time Machine (thinking that it would try to encrypt each backup as before, even though the whole drive or part-drive is already encrypted)....

and what happened is that the whole drive (or in my case the whole partition of drive) started decryption... and this was taking ages and ages!...

so then as per my post above... 'I could not find any way to cancel it (decryption). The only thing that worked was doing the same as Matthew advised for stopping an encryption process'.

so then once I'd encrypted my drive again as per Matthew's fix...

🙂 the way to do it! 🙂

I then tried the other way round (i.e. ticked/unticked) to ENable encryption (in my previously encrypted drive/partition)

then when I did a back up it was very quick/normali.e. 45mins 🙂

Hi Stuwah

it's prob too late for you but for future ref I think that there are better solutions to your original problem - see Matthew Galvin's reply and subsequent for details

AngieBongos

This absolutely worked for me! Thank you, Mathew!! 🙂

Thanks very much Matthew, this worked for me.

Works. Many thanks for posting.

Thank you, diamond solution. I assume the encryption is as strong as the Timer Machine version.

Thanks for posting this. I'm repartitioning my drive and wasn't sure if I could eject during encryption.

Hey quick question, so did you encrypt the hard drive you use for back ups and then choose to 'NOT" encrypt the time machine encryption option?? just want to make sure that that is ok to do before I go making any stupid mistakes and messing up the back up,

Thanks

Bro thanks so much for doing all the heavy lifting for this newbie to the mac system. Just fired up first Mac, an iMac. Did the encryption thing and it was horribly slow. Your method worked awesomely. Thanks Again!

Worked!! I bought a new LaCie 5T drive and backed up my 500G drive, then encrypted the LaCie for 4 DAYS. It was only halfway done. Unbelievable, right? Then I read this comment, erased the LaCie and started over using this procedure. Done and encrypted in 6 hours.

Thanks Matthew. It helps.

I got an 8TB USB3 external recently and decided to finally say yes to turning on Time Machine after formatting it. Like many others I selected activate Encryption. I have a 480GB SSD as my main drive with OS 10.10.5, Apps, and main files. I have a 750GB HDD as my secondary storage drive in place of the optical drive. So expected a 1.25TB encrypted backup to take a while. Started it Monday afternoon with a constant "13 hours remaining" all day and it transferred all through the night. Checked it Tuesday morning and it completed the backup and was at 3% encrypted, let it go all day and went to bed at 10%. Today, Wednesday, I woke up to find it at 16%. That's just too long for me so I took it to the interwebs to find out that's too long for many others. I decided to start over and try erasing and formatting with encryption as suggested. Started the new TM backup (with enabling Encryption) and it's backing up so much faster with only "4 hours remaining." So far this seems like it has been a good idea. It's already gotten past 100GB in the time I've been typing this comment. I'll know for sure after the backup is complete obviously, but I wanted to thank you for your suggestion. It seems to have helped a lot of people.