[gnirkatto]

So I gave Time Machine another try, with an external WD SSD drive. I selected encryption, for obvious reasons. The first run went well, encryption took a while but I thought OK, it has to encrypt the entire initial backup image of ~300GB. Later on I started another TM backup, which only consisted of a small number of files to be backed up incrementally.

Big surprise: after backup, it started to encrypt, and apparently it encrypted the ENTIRE SSD content again, which took a few hours!

Is there any way how to speed this up? If the only option is to always have TM encrypt an entire SSD, although only a few MB got backed up incrementally, this makes the entire system completely useless for me (unencrypted TM backups not being an option for me).

[gnirkatto]

Nobody?
Honestly, unless there is something I'm doing wrong, I consider this a significantly flawed design.
How can it be an 'incremental' TM backup takes 3 minutes only, but the subsequent encryption takes 90 minutes (or so)?

[Annie_M]

We're all volunteers here, and sometimes traffic on weekends is slow. Hopefully, someone will come along soon who can offer you some feedback.

[imwjl]

I'll be watching this because of the huge difference for my MacBook vs iMac to do this. A part of me thinks it should be faster because I don't see such a difference with Windows 10 systems using Bitlocker.

Thank you.

[gnirkatto]

We're all volunteers here, and sometimes traffic on weekends is slow. Hopefully, someone will come along soon who can offer you some feedback.

I know - and actually, this is more a discussion/exchange of experiences than a cry for help, therefore my impatience and wonder why nobody got involved yet. I just didn't find a fitting forum category to start a regular thread, therefore this "question".

[gnirkatto]

P.S. I would like to add that this is probably not an issue for someone who uses a volume that's mounted permanently as the TM drive - so TM runs in the background, mainly unnoticed, and therefore not many may get aware of long encryption runtimes.
It bothers me so much because I use a removable external SSD, and start TM manually, after mounting it. And obviously I would like to remove the SSD quickly, after backup (and encryption) complete.

[gnirkatto]

Well, now that still nobody responded, I decided to try a chat with Apple support, and here are my findings, for those who might run into the same problems now or in the future. Apologies in advance, I'm not a Mac specialist (yet?), so I will probably provide information that is obvious for more experienced users:

• the backup volume that I used was formatted as journaled, but not encrypted.
• support recommended to re-format it, journaled and encrypted. I did so.
• When mounting the newly formatted drive for the 1st time, Mac OS asked for the password that I specified during formatting the drive (which seems OK to me).
• I confirmed to store the PW in the Keychain app.
• (small sidestep into keychain management on the Mac (which felt/feels quite confusing to me): after storing the PW in the keychain, it apparently always instantly unlocks the drive on this very computer, where the PW got stored in keychain. This is very convenient but made me nervous in the beginning. Why was the volume always unlocked, immediately after mounting it? To test what's going on, I deleted the entry in keychain, re-mounted the volume and voila - got asked again to specify the encryption password (and to store it again in keychain)) - very convenient, once you figured out.)
• I selected the volume as Time Machine backup volume in TM settings, encrypt ON (it was on by default) and started the first backup. It completed successfully.
• then I unmounted the volume, updated a small Excel-file, re-mounted the volume again (no PW required ;-)), and started another TM backup.
• It said "encrypted" while running (in TM system settings) and completed in less than a minute.

So the trick is to encrypt the TM volume on the Mac OS level first, before using it for TM. If you don't encrypt it in the OS, but in TM only, it might take forever.

Why TM settings offers a switch for encryption yes or no, I do not fully understand. Maybe to make an encrypted backup on an unencrypted device that already contains other data that's supposed to remain unencrypted? Who knows.
I also don't know why Apple doesn't make users aware of OS encryption first. At least I did not run into such instructions when trying to resolve my problem. Maybe well hidden somewhere.

[Annie_M]

Thanks for the update. I am confident that the information you have shared here will be beneficial to others in the future.